Automatic redial malfunction
It's been a long time since I have used Panasonic analog phones, but the redial function in them used to be mechanical. It dialed 15 times with a 45 second pause between attempts. The key was, it expected you to pick up the handset, cancelling the redial if you got an answer.
If you got an answer and didn't do anything, it hung up and redialed again until you picked up the handset!
Could that be what your system is doing?
Carl
×