I received a broken FP2 core module a couple of days ago. After testing it was clear that the module was unable to make good contact with the screen, requiring considerable pressure to the back of the device or some slapping and twisting to get the display to work, and then only briefly.
I took the motherboard out of the core module and laid it, screen connector up, on the flat underside of an upturned glass bowl, so as to get it closer to the heating elements of my oven. I laid a small piece of solder next to the motherboard and set the oven to 200°C.
I turned on the oven and after about eight minutes, when the little length of solder turned liquid, I waited for another minute or so, turned off the oven and waited for everything to cool down completely.
I reassembled the core module, fitted it with the necessary modules and turned on the phone… and it worked! Very solid connection, no reasonable amount of percussive force or twisting seems capable of interrupting the signal.
The phone, however, ran glacially slow. I reset it to factory settings, but no luck. In the end I flashed FPOpen to the device… and now it runs like new, fast as ever.
So take from that what you will. This isn’t difficult to do and it worked for me on the first try, though of course it’s at your own risk and there’s no telling if this may brick your phone. But if you’ve got a broken old core module that you’re looking to recycle… it may be worth a try.
Thanks again to @ElKrasso for providing these instructions!