borg backup hangs on most commands after verified integrity

I have a borg backup system for some time now. The target is cloud storage, accessed by ssh. This is SSH command line from debug: SSH command line: ['ssh', '-i', '/root/.ssh/id_rsa', '-p', '23', '@.your-storagebox.de', 'borg', 'serve', '--umask=077', '--debug'] The cloud storage was full and it caused a borg prune command to stop responding. In the meantime I have killed the process for that command, deleted the borg cache, and have broken the lock. If I try to run borg info or borg check, the command stops after

Remote: Verified integrity of /home/backup/hints.8441

Here is the output of the debug:

borg check --debug 
using builtin fallback logging configuration
35 self tests completed in 0.36 seconds
SSH command line: ['ssh', '-i', '/root/.ssh/id_rsa', '-p', '23', '@.your-storagebox.de', 'borg', 'serve', '--umask=077', '--debug']
Remote: using builtin fallback logging configuration
Remote: 33 self tests completed in 0.08 seconds
Remote: using builtin fallback logging configuration
Remote: Initialized logging system for JSON-based protocol
Remote: Resolving repository path b'/./backup'
Remote: Resolved repository path to '/home/backup'
Remote: Starting repository check
Remote: Verified integrity of /home/backup/index.8441
Remote: Verified integrity of /home/backup/hints.8441

After that, the borg hangs (I have waited for a few hours now)