Could you collect a debug log?
1. Quit Telephone and run in Terminal:
defaults write com.tlphn.Telephone LogLevel -integer 4
2. Launch and use Telephone normally (or just make it sit there without any action).
3. When the problem reproduces, QUIT Telephone and send me this file:
/Users/username/Library/Containers/com.tlphn.Telephone/Data/Library/Application Support/com.tlphn.Telephone/Telephone.log
Alexey