You use softwares with auto "cleaning" settings like System/Registry Cleaners or Antivirus/Security Software?. it is a public computer?

It is my personal Computer. I used a registry cleaner once but a long time ago and it isn't installed on this system anymore, so no active cleaners running. As for antivirus, only the standard windows defender is active.

Edit: Before I reinstalled there was stuff inside the download history, but it was months old and newer downloads wouldn't show up after restarting firefox. I suspect its places.sqlite corrupting but why and even after clean reinstall?

You can check the current places.sqlite file

Type about:support in the address bar.

Scroll down and find the Places Database section.

Click the button Verify Integrity

After it runs, check the results. If it reports errors the file is corrupt. If not the issue might be an external factor preventing the save on exit.