[toptier]

My mom was complaining she would be in the middle of a phone conversation and then "someone else would get in the phone call after 5 minutes" who she didn't call nor did he/she call her.

I immediately thought she was accidentally pressing the "add a call" button, which seemed obvious, she said she wouldn't press anything...

So to show demonstrate the button to her I realized the proximity sensor does not turn off the screen, as if there was no proximity sensor at all.

Is her device a lemon, or is this a well known software issue?

[ttsoldier]

Make a call, but don't put the phone by your ear. Instead, cover the proximity sensor with your finger. The screen is supposed to turn off. If it doesn't you can try wiping the area and trying again.

If the problem still persists, perform a hard reset.

[waazzupppp]

My Evo had a problem with the prox sensor getting some dust on it. It failed to pick up when something was near it because of the dust. I had to blow it out with a can of air and then all was good. There might have been a bit of stuff that got in there by sliding under the glass near the earpiece grid.