Buttons only work on the homescreen/while typing
I recently built an older model 3G PS Vita using parts I bought on eBay. I probably could have goofed and damaged something during the assembly but all of the hardware seems to be working fine. I can use the buttons to navigate the home screen but they stop working when I open an app such as the settings app. I know there is a setting to turn off the buttons but that setting would prevent them from working on the home screen as well. Also, when I try typing something such as a WiFi password the buttons start working again but when I select a key it immediately hits enter several times and tries to connect to the access point. It doesn't do that if I tap anywhere else on the screen, only when I tap a key or select it with X. So it doesn't look like a grounding issue with the touchscreen.
Last problem is that sometimes when I press the PS Home button it thinks I'm trying to take a screenshot when I haven't pressed the start button.
These are some really weird problems and maybe some of the parts I got aren't good but I appreciate any help.