diff --git a/app/packages/looker/src/lookers/abstract.ts b/app/packages/looker/src/lookers/abstract.ts
index 08991adba9..602e4bc7f0 100644
--- a/app/packages/looker/src/lookers/abstract.ts
+++ b/app/packages/looker/src/lookers/abstract.ts
@@ -293,11 +293,6 @@ export abstract class AbstractLooker<
           return;
         }
 
-        if (this.state.destroyed && this.sampleOverlays) {
-          // close all current overlays
-          this.pluckedOverlays.forEach((overlay) => overlay.cleanup?.());
-        }
-
         if (
           !this.state.windowBBox ||
           this.state.destroyed ||
@@ -609,6 +604,7 @@ export abstract class AbstractLooker<
     this.detach();
     this.abortController.abort();
     this.updater({ destroyed: true });
+    this.sampleOverlays?.forEach((overlay) => overlay.cleanup?.());
   }
 
   disable() {
diff --git a/app/packages/looker/src/overlays/heatmap.ts b/app/packages/looker/src/overlays/heatmap.ts
index d8fb8909d5..720aa8af36 100644
--- a/app/packages/looker/src/overlays/heatmap.ts
+++ b/app/packages/looker/src/overlays/heatmap.ts
@@ -208,6 +208,7 @@ export default class HeatmapOverlay<State extends BaseState>
 
   public cleanup(): void {
     this.label.map?.bitmap?.close();
+    this.targets = null;
   }
 }
 
diff --git a/app/packages/looker/src/overlays/segmentation.ts b/app/packages/looker/src/overlays/segmentation.ts
index 04c2fc693b..f16894ca7e 100644
--- a/app/packages/looker/src/overlays/segmentation.ts
+++ b/app/packages/looker/src/overlays/segmentation.ts
@@ -263,6 +263,7 @@ export default class SegmentationOverlay<State extends BaseState>
 
   public cleanup(): void {
     this.label.mask?.bitmap?.close();
+    this.targets = null;
   }
 }
 
diff --git a/app/packages/looker/src/processOverlays.ts b/app/packages/looker/src/processOverlays.ts
index c31ee19695..789fbd84d1 100644
--- a/app/packages/looker/src/processOverlays.ts
+++ b/app/packages/looker/src/processOverlays.ts
@@ -4,6 +4,8 @@
 
 import { CONTAINS, Overlay } from "./overlays/base";
 import { ClassificationsOverlay } from "./overlays/classifications";
+import HeatmapOverlay from "./overlays/heatmap";
+import SegmentationOverlay from "./overlays/segmentation";
 import { BaseState } from "./state";
 import { rotate } from "./util";
 
@@ -30,6 +32,25 @@ const processOverlays = <State extends BaseState>(
 
     if (!(overlay.field && overlay.field in bins)) continue;
 
+    // todo: find a better approach / place for this.
+    // for instance, this won't work in detection overlay, where
+    // we might want the bounding boxes but masks might not have been loaded
+    if (
+      overlay instanceof SegmentationOverlay &&
+      overlay.label.mask_path &&
+      !overlay.label.mask
+    ) {
+      continue;
+    }
+
+    if (
+      overlay instanceof HeatmapOverlay &&
+      overlay.label.map_path &&
+      !overlay.label.map
+    ) {
+      continue;
+    }
+
     if (!overlay.isShown(state)) continue;
 
     bins[overlay.field].push(overlay);
diff --git a/app/packages/looker/src/worker/canvas-decoder.ts b/app/packages/looker/src/worker/canvas-decoder.ts
index 56749a6d2e..d0ed29f69f 100644
--- a/app/packages/looker/src/worker/canvas-decoder.ts
+++ b/app/packages/looker/src/worker/canvas-decoder.ts
@@ -1,5 +1,10 @@
 import { OverlayMask } from "../numpy";
 
+const offScreenCanvas = new OffscreenCanvas(1, 1);
+const offScreenCanvasCtx = offScreenCanvas.getContext("2d", {
+  willReadFrequently: true,
+})!;
+
 const PNG_SIGNATURE = [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a];
 /**
  * Reads the PNG's image header chunk to determine the color type.
@@ -53,20 +58,31 @@ export const decodeWithCanvas = async (blob: Blob) => {
   const imageBitmap = await createImageBitmap(blob);
   const { width, height } = imageBitmap;
 
-  const canvas = new OffscreenCanvas(width, height);
-  const ctx = canvas.getContext("2d")!;
-  ctx.drawImage(imageBitmap, 0, 0);
+  offScreenCanvas.width = width;
+  offScreenCanvas.height = height;
+
+  offScreenCanvasCtx.drawImage(imageBitmap, 0, 0);
+
   imageBitmap.close();
 
-  const imageData = ctx.getImageData(0, 0, width, height);
+  const imageData = offScreenCanvasCtx.getImageData(0, 0, width, height);
 
   if (channels === 1) {
     // get rid of the G, B, and A channels, new buffer will be 1/4 the size
-    const data = new Uint8ClampedArray(width * height);
-    for (let i = 0; i < data.length; i++) {
-      data[i] = imageData.data[i * 4];
+    const rawBuffer = imageData.data;
+    const totalPixels = width * height;
+
+    let read = 0;
+    let write = 0;
+
+    while (write < totalPixels) {
+      rawBuffer[write++] = rawBuffer[read];
+      // skip "G,B,A"
+      read += 4;
     }
-    imageData.data.set(data);
+
+    const grayScaleData = rawBuffer.slice(0, totalPixels);
+    rawBuffer.set(grayScaleData);
   }
 
   return {
diff --git a/app/packages/spotlight/src/createScrollReader.ts b/app/packages/spotlight/src/createScrollReader.ts
index d164f1b5ab..0a1abfbf39 100644
--- a/app/packages/spotlight/src/createScrollReader.ts
+++ b/app/packages/spotlight/src/createScrollReader.ts
@@ -9,6 +9,7 @@ export default function createScrollReader(
   render: (zooming: boolean, dispatchOffset?: boolean) => void,
   getScrollSpeedThreshold: () => number
 ) {
+  let animationFrameId: ReturnType<typeof requestAnimationFrame>;
   let destroyed = false;
   let prior: number;
   let scrolling = false;
@@ -63,7 +64,7 @@ export default function createScrollReader(
       updateScrollStatus();
     }
 
-    requestAnimationFrame(animate);
+    animationFrameId = requestAnimationFrame(animate);
   };
 
   animate();
@@ -73,6 +74,14 @@ export default function createScrollReader(
       destroyed = true;
       element.removeEventListener("scroll", scroll);
       element.removeEventListener("scrollend", scrollEnd);
+
+      if (timeout) {
+        clearTimeout(timeout);
+      }
+
+      if (animationFrameId) {
+        cancelAnimationFrame(animationFrameId);
+      }
     },
     zooming: () => zooming,
   };