Synchronisation to Android

I am using Joplin on a Linux Mint 20.4 system and 2 Android phones. Dropbox-synch, File-size some 0.5 GB. All devices are on the latest versionsl (2.11.11 on LInux). After I had to reinstall on LInux I have a devastating experience. An example: I reinstalled on Linux and imported a 3 day old Jex-File. Result: everything was resynchronized from Dropbox, creating double entries. After I deleted the double entries, the Android phones started a resync-orgy that is still going on.
I had similar experiences several times lately.

Please provide a simple means to push some files (database, ressources, zipped or even a *.jex-File) to the phone and reset the application from these files. The code should basically exist. I am sorry I have no time to familiarize with the Joplin-Universe to implement that myself.
Best regards