If you have sync, and there is a problem anywhere, '''Shut Down Sync Immediately On All Devices''' to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again. [v57+] Places Maintenance is built into Firefox. Type '''about:support'''<enter> in the address bar. You will find '''Places Database''' near the bottom. Press the '''Verify Integrity''' button. When done, copy and post the results here.