Database error: "sql: transaction has already been committed or rolled back"

Which version of LXD did these occur on? I ran into some of the same DB and timeout messages, specifically related to LXD 5.3. If your issues were on some other version, it is not related.

Details here: Timeouts after upgrading to LXD 5.3

If your version is 5.3, the workaround may be just a small downgrade:
sudo snap revert lxd