Symptom:
New call window can not be opened during duration test

Conditions:
1. Phone A calls phone B. Phone B answers.
2. Phone B transfers the call to phone C.
3. Phone C ends the call.
4. Repeat.
After one-night test, phone A can't make calls. Soft key New Call, pressing idle session key, hooking-off, pressing the speaker button and pressing digit buttons don't invoke new call window.
But the Application button, the Directory button, the Message button work.