Recent History Missing/Flakey

Add-ons Add-on Support
#1
  1. FF History recently became flakey / missing (FF ESR 52.9.0 Retro for XP)
    Most recent History (FF used daily) was May 16 (today = June 3)
  2. Attempted to resolve this with “Places Maintenance” by MaK77
  3. Websearches for above prompt “huh” “whaaat” and “may have been removed, but we’re not sure exactly what happened …” [seems just a bit vague/unhelpful]
  4. Anyhoo - as of this writing, FF History seems to have “recuperated” - but who knows for how long.
  5. Anyone have a link to to a clear, concise process by which I can troubleshoot & hopefully resolve future History issues (bookmarks well-behaved AFAIK)

Aside - encouraging (I guess) that AI is also subject to “brain farts”. Forum interpolator popped-up this gem:
" Your topic is similar to…Gibberish inference result when using pre-trained model for unknown distribution …"
Actually kinda made my day!

#2

If you open Help > Troubleshooting Information, did Firefox 52 ESR have the Verify Integrity feature toward the bottom of the page? Some of the major functions of the extension were integrated into Firefox there.