Server down because of Multiple Database Compact - Please Help

hi all, one of our databases is compacted overnight automatically. Today the compact-task was running during the day. Than a second compact-task for the same database started and a third one. We now restarted the server (server performance down), but the task immediately restarted, so now we stopped it manually (But it restarts again !). Its a large Database (~50 GByte). May be the cause is we archived yesterday ~8GByte attachments in a replica. But why multiple compactor tasks for the same database and why they never ended running?

Thank you very much for any hint