CDMA Doesn't Charge Sometimes

[ChappyEight]

Okay, here's the situation.

My wife purchased a Sprint Touch Pro in February for her job. Everything was fine for a couple months but then it randomly would not charge overnight. Basically, the white LED's would indicate it was fully charged, then you'd start the phone up and battery would be critically low.

Now, there was also a funky twist. Sometimes the phone actually would be charged but the battery indicator on screen would show the critically low icon. When you click on the icon, it would say that the battery status was unknown.

So, after 4 visits to Sprint and a few phone calls, they finally replaced the phone yesterday.

This morning she turns the phone on after charging overnight and the battery indicator shows the critically low icon. When clicked upon, it states that the battery level is unknown. WTF?? It appears to have charge, but the indicator is f'd.

The phone is plain jane stock right now, I've not tweaked/hacked it in any way.

Any ideas on what could be causing this issue? The Sprint techs are clueless and keep changing batteries. After the 3rd battery, you'd think they'd figure out that's not the problem.

Thanks in advance.