Dump Transaction Log hanging

Hi experts

we have the following situation.

We have hanging DUMP TRANSACTION processes and if we don't get it in conroll the system might get stop the system, as the log gets filled.

The dump transaction is hanging with "Wait Event" "waiting for mass destruction to complete".

If I check the <SID>_BS.log I don't see ANY message regarding the dump it self.
What is really strange, as I also don't see in the log that it did start the backup.

The SQL Statement to be executed is "set notcount on set flushmessage on dump transaction <SID> to "<backup target>" with notify = client

Does anybody have an idea what I can do?

Kind regards