on what version are you? [HOWTO] Give complete /e/OS version info easily for support, answers, comparison etc
can’t see a current/open bug that describes the behaviour - https://gitlab.e.foundation/e/backlog/-/issues/?label_name[]=eDrive
The app-passwords do not expire, so I have no explanation either.
Can you describe what defines being unreliable - new photos do not show up after x minutes? there are hardcoded intervals and it depends if the device finds an unmetered connection, see Murena 2 not synching files - #3 by tcecyk