diff --git a/apps/readest-app/src/app/reader/hooks/useProgressSync.ts b/apps/readest-app/src/app/reader/hooks/useProgressSync.ts
index f03da01a..dee3a823 100644
--- a/apps/readest-app/src/app/reader/hooks/useProgressSync.ts
+++ b/apps/readest-app/src/app/reader/hooks/useProgressSync.ts
@@ -134,11 +134,15 @@ export const useProgressSync = (bookKey: string) => {
           content?.index,
           bookData.bookDoc,
         );
-        if (CFI.compare(remoteCFILocation, candidateCFI) < 0) {
+        if (!remoteCFILocation || CFI.compare(remoteCFILocation, candidateCFI) < 0) {
           remoteCFILocation = candidateCFI;
         }
       }
-      setConfig(bookKey, syncedConfig);
+      const filteredSyncedConfig = Object.fromEntries(
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars
+        Object.entries(syncedConfig).filter(([_, value]) => value !== null && value !== undefined),
+      );
+      setConfig(bookKey, { ...config, ...filteredSyncedConfig });
       if (remoteCFILocation && configCFI) {
         if (CFI.compare(configCFI, remoteCFILocation) < 0) {
           if (view) {
diff --git a/apps/readest-app/src/hooks/useSync.ts b/apps/readest-app/src/hooks/useSync.ts
index 0d123b66..0762b9bc 100644
--- a/apps/readest-app/src/hooks/useSync.ts
+++ b/apps/readest-app/src/hooks/useSync.ts
@@ -33,6 +33,7 @@ const computeMaxTimestamp = (records: BookDataRecord[]): number => {
   return maxTime;
 };
 
+const ONE_DAY_IN_MS = 24 * 60 * 60 * 1000;
 export function useSync(bookKey?: string) {
   const router = useRouter();
   const { settings, setSettings } = useSettingsStore();
@@ -77,10 +78,15 @@ export function useSync(bookKey?: string) {
     const lastSyncedConfigsAt = config?.lastSyncedAtConfig ?? settings.lastSyncedAtConfigs ?? 0;
     const lastSyncedNotesAt = config?.lastSyncedAtNotes ?? settings.lastSyncedAtNotes ?? 0;
     const now = Date.now();
-    const fullSyncThreshold = 3 * 24 * 60 * 60 * 1000;
-    setLastSyncedAtBooks(now - lastSyncedBooksAt > fullSyncThreshold ? 0 : lastSyncedBooksAt);
-    setLastSyncedAtConfigs(now - lastSyncedConfigsAt > fullSyncThreshold ? 0 : lastSyncedConfigsAt);
-    setLastSyncedAtNotes(now - lastSyncedNotesAt > fullSyncThreshold ? 0 : lastSyncedNotesAt);
+    setLastSyncedAtBooks(
+      now - lastSyncedBooksAt > 3 * ONE_DAY_IN_MS ? 0 : lastSyncedBooksAt - ONE_DAY_IN_MS,
+    );
+    setLastSyncedAtConfigs(
+      now - lastSyncedConfigsAt > 3 * ONE_DAY_IN_MS ? 0 : lastSyncedConfigsAt - ONE_DAY_IN_MS,
+    );
+    setLastSyncedAtNotes(
+      now - lastSyncedNotesAt > 3 * ONE_DAY_IN_MS ? 0 : lastSyncedNotesAt - ONE_DAY_IN_MS,
+    );
     setLastSyncedAtInited(true);
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [bookKey, settings, config]);