Has anyone else had this problem?

Had the Sprint Franken Pre 2 for a month or so. I have the screen lock on and it activates when idle for 5 minutes.

This past week, when I have the Pre 2 on the Touchstone and a call comes in while the screen is locked, as soon as I answer the call, it hangs up.

I think it might have happened a few times when the Pre 2 was not on the TS, too. I don't think this happens when I'm using my Bluetooth earpiece.

I checked the phone preferences and there doesn't seem to be anything related to this in there.

Any suggestions on what's going on?