I am experiencing the same problem using the microsoft365 connector.

When I am in a teams call and teams sets the myapps presence to busy, then call forwardings by busy do not work.

What's really weird about it is, that the Caller gets a busy tone, while my myapps softphone does signal me the call actually but when I accept the call, nobody is there of course because the caller already hung up.

So neither does the call forwarding work, nor does the busy signalling really work as intended.