Issue Internal error Dropbox-backup plugin

[svh1985]

Hi there,

I'm getting errors from the offsite Dropbox backup plugin:
Server
Plesk entry point: https://server.com:8443/

The following error occurred during the scheduled backup process:

Transport error: Extension transport: ext://dropbox-backup/server/: {"error": "Internal Server Error"}

I've searched for solutions in the knowledge-base but could not find any hints or solutions for this specific error.
All solutions, like cleaning the sqllite db, I found did not solve the issue.