If your phone rings and when you pickup disconnects all parties, it is most probably an asterisk bug, not related to the fop2 upgrade. What it is broken in 2.21 is transfers to external numbers. In any case, you must run fop2_server in debug mode level 15 and capture the output when you perform a spy session or whisper session. That output will help us know if fop2 is sending correct commands to the AMI or not. The whisper action in itself does not perform any disconnect program, that is why I am almost positive that is an asterisk bug.