both nextcloud-client and eDrive aren’t two-way-sync, there is an old thread on it if you want to dive in the forum, or the long 2-way sync thread in nextcloud issues.
I think what the eDrive app cache/storage reset can help with is when the sqlite internal state of device-to-cloud gets into a unrecoverable state. Resetting makes it scanning for a new local/remote list. Interesting this didn’t work out for you either.