I have a StarTAC 7868 on Pageplus and it recently started shutting off once the phone gets opened a certain amount. If I open the phone to just the point where this occurs and then quickly lower it some, then it will come back and say "searching" and it gets a signal a few seconds later. If I don't do that and just open the phone all the way, it will not come back on until I partially close it and then power on. The phone will not even turn on at all unless it is partially closed.
I thought the ribbon cable may be loose, so I opened the phone up, cleaned the connectors and plugged it back in, but that didn't help any. I tried using the phone without the battery using just the charger and it does not have this issue. Could the problem just be the battery, or is it something else in the upper half of the phone?
I had a StarTAC 10 years ago. My guess is that the ribbon cable has a break where it passes through the hinge. The break opens up and kills the connection between the battery and the main circuit board in the phone when the flip is opened. The charger plugs directly into the main circuit board. That's why the phone doesn't act up when it's on the charger. I had similar problems with the earpiece audio cutting out and it was caused by a bad ribbon cable.