diff --git a/vite/src/pipedal/Pedalboard.tsx b/vite/src/pipedal/Pedalboard.tsx
index 56b9d94..1012687 100644
--- a/vite/src/pipedal/Pedalboard.tsx
+++ b/vite/src/pipedal/Pedalboard.tsx
@@ -394,6 +394,7 @@ export class Pedalboard implements Deserializable<Pedalboard> {
     pathProperties: {[Name: string]: string} = {};
     selectedPlugin: number = -1;
 
+    // yields all items in the pedalboard, including split items. Splits are yielded before their children.
     *itemsGenerator(): Generator<PedalboardItem, void, undefined> {
         let it = itemGenerator_(this.items);
         while (true)
@@ -403,6 +404,16 @@ export class Pedalboard implements Deserializable<Pedalboard> {
             yield v.value;
         }
     }
+    // same as itemsGenerator, but yields split items after their chains.
+    *itemsGeneratorSplitAfter(): Generator<PedalboardItem, void, undefined> {
+        let it = itemGeneratorSplitAfter_(this.items);
+        while (true)
+        {
+            let v = it.next();
+            if (v.done) break;
+            yield v.value;
+        }
+    }
 
     makeSnapshot(): Snapshot {
         let result = new Snapshot();
@@ -793,4 +804,28 @@ function* itemGenerator_(items: PedalboardItem[]): Generator<PedalboardItem, voi
     }
 }
 
+function* itemGeneratorSplitAfter_(items: PedalboardItem[]): Generator<PedalboardItem, void, undefined> {
+    for (let i = 0; i < items.length; ++i) {
+        let item = items[i];
+        if (item.uri === SPLIT_PEDALBOARD_ITEM_URI) {
+
+            let splitItem = item as PedalboardSplitItem;
+
+            let it = itemGenerator_(splitItem.topChain);
+            while (true) {
+                let v = it.next();
+                if (v.done) break;
+                yield v.value;
+            }
+            it = itemGenerator_(splitItem.bottomChain);
+            while (true) {
+                let v = it.next();
+                if (v.done) break;
+                yield v.value;
+            }
+        }
+        yield item;
+    }
+}
+
 
diff --git a/vite/src/pipedal/PiPedalModel.tsx b/vite/src/pipedal/PiPedalModel.tsx
index b2c478f..7f4fd54 100644
--- a/vite/src/pipedal/PiPedalModel.tsx
+++ b/vite/src/pipedal/PiPedalModel.tsx
@@ -659,6 +659,7 @@ export class PiPedalModel //implements PiPedalModel
     }
 
     private setModelPedalboard(pedalboard: Pedalboard) {
+        this.removeInvalidSidechains(pedalboard);
         this.pedalboard.set(pedalboard);
         this.selectedSnapshot.set(pedalboard.selectedSnapshot);
         this.updateEnabledItems(pedalboard);
@@ -1763,13 +1764,17 @@ export class PiPedalModel //implements PiPedalModel
         }
 
         let it = newPedalboard.itemsGenerator();
+        let oldInstanceId = -1;
+        let newInstanceId = -1;
         while (true) {
             let v = it.next();
             if (v.done) break;
             let item = v.value;
             if (item.instanceId === itemId) {
+                oldInstanceId = item.instanceId;
                 item.deserialize(new PedalboardItem()); // skeezy way to re-initialize.
                 item.instanceId = ++newPedalboard.nextInstanceId;
+                newInstanceId = item.instanceId;
                 item.uri = selectedUri;
                 item.pluginName = plugin.name;
                 item.controlValues = this.getDefaultValues(item.uri);
@@ -1784,6 +1789,9 @@ export class PiPedalModel //implements PiPedalModel
                     item.pathProperties[fileProperty.patchProperty] = "null";
                 }
                 newPedalboard.selectedPlugin = item.instanceId;
+                if (oldInstanceId !== -1) {
+                    this.updateSidechainReferences(newPedalboard, oldInstanceId, newInstanceId);
+                }
                 this.setModelPedalboard(newPedalboard);
                 this.updateServerPedalboard()
                 return item.instanceId;
@@ -1938,6 +1946,9 @@ export class PiPedalModel //implements PiPedalModel
         newPedalboard.replaceItem(fromInstanceId, emptyItem);
         newPedalboard.replaceItem(toInstanceId, fromItem);
         newPedalboard.selectedPlugin = fromItem.instanceId;
+        if (!toItem.isEmpty()) {
+            this.updateSidechainReferences(newPedalboard, toItem.instanceId, fromItem.instanceId);
+        }
         this.setModelPedalboard(newPedalboard);
         this.updateServerPedalboard();
 
@@ -3545,29 +3556,67 @@ export class PiPedalModel //implements PiPedalModel
 
     }
     requestBankPresets(bankInstanceId: number): Promise<PresetIndexEntry[]> {
-        return nullCast(this.webSocket).request<PresetIndexEntry[]>("requestBankPresets", {bankInstanceId: bankInstanceId});
-    }   
+        return nullCast(this.webSocket).request<PresetIndexEntry[]>("requestBankPresets", { bankInstanceId: bankInstanceId });
+    }
 
     importPresetsFromBank(bankInstanceId: number, presets: number[]): Promise<number> {
-        return nullCast(this.webSocket).request<number>("importPresetsFromBank", {bankInstanceId: bankInstanceId, presets: presets});
+        return nullCast(this.webSocket).request<number>("importPresetsFromBank", { bankInstanceId: bankInstanceId, presets: presets });
     }
     copyPresetsToBank(bankInstanceId: number, presets: number[]): Promise<number> {
-        return nullCast(this.webSocket).request<number>("copyPresetsToBank", {bankInstanceId: bankInstanceId, presets: presets});
+        return nullCast(this.webSocket).request<number>("copyPresetsToBank", { bankInstanceId: bankInstanceId, presets: presets });
     }
     setPedalboardSideChainInput(instanceId: number, sideChainInputId: number): void {
         let pedalboard = this.pedalboard.get().clone();
         let pedalboardItem = pedalboard.getItem(instanceId);
-        if (!pedalboardItem)
-        {
+        if (!pedalboardItem) {
             return;
         }
         pedalboardItem.sideChainInputId = sideChainInputId;
-        pedalboardItem.instanceId = ++pedalboard.nextInstanceId;
+        let oldId = pedalboardItem.instanceId;
+        let newId = ++pedalboard.nextInstanceId;
+
+        pedalboardItem.instanceId = newId; // force reload of pedalboard.
         pedalboard.selectedPlugin = pedalboardItem.instanceId;
+
+        this.updateSidechainReferences(pedalboard, oldId, newId);
         this.setModelPedalboard(pedalboard);
         this.updateServerPedalboard();
 
     }
+
+    removeInvalidSidechains(pedalboard: Pedalboard) {
+        let it = pedalboard.itemsGeneratorSplitAfter();
+        let previousItemIds: Set<number> = new Set<number>();
+        previousItemIds.add(-2); // start is visible.
+        while (true) {
+            let r = it.next();
+            if (r.done) {
+                break;
+            }
+            let item = r.value;
+            if (item.sideChainInputId !== -1) {
+                if (!previousItemIds.has(item.sideChainInputId)) {
+                    item.sideChainInputId = -1;
+                }
+            }
+            if (!item.isEmpty()) { // empty items are not valid sidechain targets.
+                previousItemIds.add(item.instanceId);
+            }
+        }
+    }
+    updateSidechainReferences(pedalboard: Pedalboard, oldItemId: number, newItemId: number) {
+        let it = pedalboard.itemsGenerator();
+
+        while (true) {
+            let r = it.next();
+            if (r.done) break;
+            let item = r.value;
+            if (item.sideChainInputId === oldItemId) {
+                item.sideChainInputId = newItemId;
+            }
+        }
+        this.removeInvalidSidechains(pedalboard);
+    }
 };
 
 let instance: PiPedalModel | undefined = undefined;
diff --git a/vite/src/pipedal/SnapshotEditor.tsx b/vite/src/pipedal/SnapshotEditor.tsx
index 5708b44..5bb0110 100644
--- a/vite/src/pipedal/SnapshotEditor.tsx
+++ b/vite/src/pipedal/SnapshotEditor.tsx
@@ -24,7 +24,7 @@ import CloseIcon from '@mui/icons-material/Close';
 import AppBar from '@mui/material/AppBar';
 import Toolbar from '@mui/material/Toolbar';
 import CssBaseline from '@mui/material/CssBaseline';
-import {createStyles} from './WithStyles';
+import { createStyles } from './WithStyles';
 
 import { withStyles } from "tss-react/mui";
 import IconButtonEx from './IconButtonEx';
@@ -148,10 +148,12 @@ const SnapshotEditor = withStyles(
 
             this.model_.zoomedUiControl.addOnChangedHandler(
                 () => {
-                    this.setState({
-                        zoomedControlOpen: this.model_.zoomedUiControl.get() !== undefined,
-                        zoomedControlInfo: this.model_.zoomedUiControl.get()
-                    });
+                    if (this.mounted93) {
+                        this.setState({
+                            zoomedControlOpen: this.model_.zoomedUiControl.get() !== undefined,
+                            zoomedControlInfo: this.model_.zoomedUiControl.get()
+                        });
+                    }
                 }
             );
 
@@ -182,9 +184,11 @@ const SnapshotEditor = withStyles(
             this.setState({ isFullScreen: !this.state.isFullScreen });
         }
 
+        private mounted93: boolean = false;
         componentDidMount() {
 
             super.componentDidMount();
+            this.mounted93 = true;
             this.model_.showStatusMonitor.addOnChangedHandler(this.showStatusMonitorHandler);
 
         }
@@ -206,6 +210,7 @@ const SnapshotEditor = withStyles(
         }
 
         componentWillUnmount() {
+            this.mounted93 = false;
             super.componentWillUnmount();
             this.model_.banks.removeOnChangedHandler(this.showStatusMonitorHandler);
         }