DB Backup process doesn't stop anymore. How to kill it?

Dear Youtrack-Support,

I realised that the automatic database backup process once didn't stop anymore although the related backup file is already created. The hour glass is still circling and any administration settings cannot be changed. I always get the error message "The service is currently under maintenance and is working in the read-only mode...".
If I don't stop it manually it will never stop.

How can this happen? And how I can kill this (cron?) job?
Even a restart of my locally running Youtrack doesn't work. I assume it is prevented from stopping by the cron job, is it?...

I would appreciate any help from you.
Thank you so much!!