diff --git a/website/src/features/toolboxes/modules/RngSimulatorModule.jsx b/website/src/features/toolboxes/modules/RngSimulatorModule.jsx
index 0c741cd..918acb2 100644
--- a/website/src/features/toolboxes/modules/RngSimulatorModule.jsx
+++ b/website/src/features/toolboxes/modules/RngSimulatorModule.jsx
@@ -146,7 +146,8 @@ function getToneFromDelta(value) {
 }
 
 export function RngSimulatorModule({ toolboxId, moduleId, context, editing = false, setEditing = () => {}, textExchangeOpen }) {
-  const data = context.normalizeRngSimulatorData(context.getModuleData(toolboxId, moduleId, {}));
+  const rawData = context.getModuleData(toolboxId, moduleId, {});
+  const data = useMemo(() => context.normalizeRngSimulatorData(rawData), [context, rawData]);
   const textContent = context.moduleText?.rngSimulator || {};
   const tabs = useMemo(() => [
     { ...RNG_TABS[0], label: textContent.trackingTabLabel || RNG_TABS[0].label },
diff --git a/website/src/features/toolboxes/modules/TimerModule.jsx b/website/src/features/toolboxes/modules/TimerModule.jsx
index fa18b52..b65b491 100644
--- a/website/src/features/toolboxes/modules/TimerModule.jsx
+++ b/website/src/features/toolboxes/modules/TimerModule.jsx
@@ -31,16 +31,20 @@ import {
 } from "./timerOptions.js";
 
 export function TimerModule({ toolboxId, moduleId, context, textExchangeOpen }) {
-  const data = context.normalizeTimerData(context.getModuleData(toolboxId, moduleId, { activeTab: "stopwatch" }));
+  const rawData = context.getModuleData(toolboxId, moduleId, { activeTab: "stopwatch" });
+  const data = useMemo(() => context.normalizeTimerData(rawData), [context, rawData]);
   const textContent = context.moduleText?.timer || {};
   const activeTab = data.activeTab;
   const [nowMs, setNowMs] = useState(getNowMs);
   const countdownDraft = useDraftForm(DEFAULT_COUNTDOWN_FORM);
 
+  const clockActive = Boolean(data.stopwatch.startedAt || data.countdowns.some((countdown) => countdown.autoRefresh));
+
   useEffect(() => {
+    if (!clockActive) return undefined;
     const intervalId = window.setInterval(() => setNowMs(getNowMs()), 50);
     return () => window.clearInterval(intervalId);
-  }, []);
+  }, [clockActive]);
 
   const stopwatchElapsedMs = data.stopwatch.startedAt
     ? data.stopwatch.elapsedMs + Math.max(0, nowMs - data.stopwatch.startedAt)
diff --git a/website/src/features/toolboxes/modules/useGoalTreeController.js b/website/src/features/toolboxes/modules/useGoalTreeController.js
index f64b7d2..0024ea5 100644
--- a/website/src/features/toolboxes/modules/useGoalTreeController.js
+++ b/website/src/features/toolboxes/modules/useGoalTreeController.js
@@ -20,7 +20,8 @@ import {
 } from "./goalTreeUtils.js";
 
 export function useGoalTreeController({ toolboxId, moduleId, context, editing, setEditing, openEditor }) {
-  const data = context.normalizeGoalTreeData(context.getModuleData(toolboxId, moduleId, { nodes: [] }));
+  const rawData = context.getModuleData(toolboxId, moduleId, { nodes: [] });
+  const data = useMemo(() => context.normalizeGoalTreeData(rawData), [context, rawData]);
   const textContent = context.moduleText?.goalTree || {};
   const treeOrientation = data.orientation || "horizontal";
   const verticalView = treeOrientation === "vertical";