Recently, my iPhone 4's headphones won't stay seated in the jack. I'll push them in firmly, and then a few seconds later (without touching the phone, the headphones, or anything else), they'll pop back out – just enough to no longer make contact, pausing audio playback.
I first I thought it was the headphones themselves, but I've tried an older pair of iPod headphones (without the clicker), and the same thing happens, although not as badly.
If I fiddle enough with either pair, I can eventually get them to stay seated, but I can't tell what it is that makes them stay in on one particular attempt vs. another.
Is there anything I can do? The jack appears to be free of any dust/lint – should I try blowing it with some compressed air? I can't imagine that it's physically damaged on the inside, but I don't know why else the plug would pop out.