diff --git a/engage-api/get-activity.ts b/engage-api/get-activity.ts
index ce0f3d2..1a6b982 100644
--- a/engage-api/get-activity.ts
+++ b/engage-api/get-activity.ts
@@ -45,6 +45,7 @@ async function getCompleteCookies(userName: string, userPwd: string): Promise<st
 
 /**
  * Get activity details from API
+ * Only returns data on HTTP 200. Returns null on any error (5xx, timeout, etc.)
  */
 async function getActivityDetailsRaw(
   activityId: string,
@@ -73,6 +74,16 @@ async function getActivityDetailsRaw(
         // Add additional timeout safety
         maxRedirects: 5
       });
+      
+      // CRITICAL: Only accept HTTP 200. Reject all other status codes including 5xx
+      if (response.status !== 200) {
+        logger.error(`Non-200 status ${response.status} for activity ${activityId}. NOT updating cache to preserve local data.`);
+        if (attempt === maxRetries - 1) {
+          logger.error(`All ${maxRetries} retries failed with non-200 status for activity ${activityId}.`);
+        }
+        return null;
+      }
+      
       logger.debug(`Attempt ${attempt + 1}/${maxRetries} for activity ${activityId} - Received response status ${response.status}`);
       const outerData = JSON.parse(response.data);
       if (outerData && typeof outerData.d === 'string') {
@@ -88,7 +99,7 @@ async function getActivityDetailsRaw(
     } catch (error: any) {
       // Only treat 401 (Unauthorized) and 403 (Forbidden) as authentication errors
       // 404 (Not Found) is valid - activity doesn't exist
-      // Other 4xx errors should not trigger re-authentication
+      // Other 4xx/5xx errors should not trigger re-authentication
       if (error.response && (error.response.status === 401 || error.response.status === 403)) {
         logger.warn(`Authentication error (${error.response.status}) while fetching activity ${activityId}. Cookie may be invalid.`);
         throw new AuthenticationError(`Received ${error.response.status} for activity ${activityId}`, error.response.status);
@@ -97,6 +108,10 @@ async function getActivityDetailsRaw(
 
       if (error.response) {
         logger.error(`Status: ${error.response.status}, Data (getActivityDetailsRaw): ${ String(error.response.data).slice(0,100)}...`);
+        // CRITICAL: 5xx errors should NOT update cache
+        if (error.response.status >= 500 && error.response.status < 600) {
+          logger.error(`Server error ${error.response.status} - preserving local cache, not updating.`);
+        }
       }
       if (attempt === maxRetries - 1) {
         logger.error(`All ${maxRetries} retries failed for activity ${activityId}.`);
diff --git a/services/cache-manager.ts b/services/cache-manager.ts
index f6e85ca..feb3f89 100644
--- a/services/cache-manager.ts
+++ b/services/cache-manager.ts
@@ -72,9 +72,10 @@ let skippedCount = 0;
 /**
  * Process and cache a single activity
  * @param activityId - The activity ID to process
+ * @param forceUpdate - If true, update cache even on fetch failure (default: false)
  * @returns The processed activity data
  */
-async function processAndCacheActivity(activityId: string): Promise<ActivityData> {
+async function processAndCacheActivity(activityId: string, forceUpdate: boolean = false): Promise<ActivityData> {
   logger.debug(`Processing activity ID: ${activityId}`);
   try {
     if (!USERNAME || !PASSWORD) {
@@ -92,11 +93,21 @@ async function processAndCacheActivity(activityId: string): Promise<ActivityData
     let structuredActivity: ActivityData;
 
     if (!activityJson) {
-      logger.info(`No data found for activity ID ${activityId} from engage API. Caching as empty.`);
-      structuredActivity = { 
-        lastCheck: new Date().toISOString(), 
-        source: 'api-fetch-empty' 
-      };
+      // CRITICAL: Only cache empty data if forceUpdate is true
+      // This prevents 5xx errors from overwriting valid local data
+      if (forceUpdate) {
+        logger.info(`No data found for activity ID ${activityId} from engage API. Force updating cache.`);
+        structuredActivity = { 
+          lastCheck: new Date().toISOString(), 
+          source: 'api-fetch-empty' 
+        };
+        await setActivityData(activityId, structuredActivity);
+        return structuredActivity;
+      } else {
+        logger.warn(`No data for activity ${activityId}. Preserving existing cache - NOT updating.`);
+        const existingData = await getActivityData(activityId);
+        return existingData || { lastCheck: new Date().toISOString(), source: 'cache-preserved' };
+      }
     } else {
       structuredActivity = await structActivityData(activityJson);
       if (structuredActivity && structuredActivity.photo && 
@@ -124,12 +135,19 @@ async function processAndCacheActivity(activityId: string): Promise<ActivityData
     return structuredActivity;
   } catch (error) {
     logger.error(`Error processing activity ID ${activityId}:`, error);
-    const errorData: ActivityData = { 
-      lastCheck: new Date().toISOString(), 
-      error: "Failed to fetch or process" 
-    };
-    await setActivityData(activityId, errorData);
-    return errorData;
+    // CRITICAL: On error, preserve existing cache instead of overwriting with error data
+    if (forceUpdate) {
+      const errorData: ActivityData = { 
+        lastCheck: new Date().toISOString(), 
+        error: "Failed to fetch or process" 
+      };
+      await setActivityData(activityId, errorData);
+      return errorData;
+    } else {
+      logger.warn(`Error fetching activity ${activityId}. Preserving existing cache.`);
+      const existingData = await getActivityData(activityId);
+      return existingData || { lastCheck: new Date().toISOString(), error: (error as Error).message };
+    }
   }
 }