SSH connection not closed

[EugenMayer]

After connecting to an SSH server and then disconnecting (exit) the connection is not closed (ps aux | grep ssh).
Also flushing with ass socket flush does not help.

My problem is that I used quiet some port forwarding and keeping those connections in the backup does block me from using the same port for a different connection

tried it with enabled or disable keepalive

  TCPKeepAlive: yes
  ServerAliveInterval: 15
  ServerAliveCountMax: 3

Is this related to

  ControlMaster: auto
  ControlPath: ~/.ssh/sockets/%h-%p-%r.sock
  ControlPersist: yes

I though the latter is rather for connection reused and should be closed when running ass socket flush

Latest stable arch / assh version v2.11.3 (281772c0)