Phone looses power when recieving calls

[Guest humz]

Had my phone decertified for a month or so now but I've noticed that since I got it done, my phone turns itself off whenever someone phones me and the battery is half dead. It turns off in the same way it does when you take off the battery without turning it off first - the image stays on the screen for a while and then gradually fades. Its pretty annoying because it turns off before the phone starts ringing so I rarely know when its happened and so my phone stays off for ages and people keep thinking I'm turning my phone off to avoid them. Has anyone else encountered this problem? It could be due to an unsigned app running on my phone but I have so many it could be any of them.

I have an SPV and my ROM is 1.3.5.6.