FP3 dies during bootup

Hey there,

I have the following issue and am not sure what to do and whether it is a HW or a SW problem:

I have a FP3 which dies during bootup shortly after the Fairphone logo disappears and the boot animation starts. The effect happened after an update. I reinstalled the official FP OS with fastboot a few times now with the very same effect. My last try was installing DivestOS but it turned out just the same. The installation scripts don’t report me any issue or warning. I can access fastboot as well as recovery mode and can perform a factory reset there (with no change to the situation).

Here comes the weird thing: when I insert another FP3 battery, I can’t get into neither fastboot nor recovery mode. The phone vibrates shortly (and dies?) and then vibrates shortly again and boots into system. This battery works fine though in another FP3…

Some details about the mainboard: the spring connector which is marked in the picture got teared away (I still have it and could try to resolder it) and some of the metal shielding on it is lose on one side. Is it worth it to try fixing these details?

Best regards,
Clemens