My GoPro was constantly freezing up and corrupting files if I was recording. GoPro said it was out of warranty and the best they could do is give me a 20% discount code for a new GoPro.
After a bunch of research, I decided that it was probably the image sensor. I bought a new one from eBay (since iFixit didn't have any in stock), but after installing it, I had the same issues. So I figured at that point, it must be the motherboard.
It's a pretty painless repair if you have worked with small electronics before. I've taken this one apart a number of times, so I was pretty familiar with how it comes apart.
Be careful of the tiny ribbon cable on the left side after you open it up. It comes out really easily. Also there is a power cable on the left side that comes out from the board, so don't just pull on it.