The log (via www), since server restart, contains only this at a level >= 1:
{"reqId":"AJymyt5Ns8sSbxzC8DpM","level":1,"time":"2022-05-20T10:12:02+00:00","remoteAddr":"","user":"--","app":"cron","method":"--","url":"--","message":"Invalidating tokens older than 2022-05-20T09:52:02+00:00"}
Then there is another log printed via docker-compose logs --follow owncloud which shows a lot of www GET access data, but does not seem to report any errors.