I am seeing this issue - places.sqlite is being corrupted when cookie is running, and appears to be remaining OK when cookie has been quit (and places.sqlite deleted and rebuilt by Firefox).
Firefox version is 70.0.2, Cookie version is 6.0.6
Easiest way to see this is to go to Help->Troubleshooting and find Places Database, and click the Verify Integrity button - which appears to show that the database is corrupt on disk.
- Nigel