Okay, i was too ambitious. Turns out i wanted to squeeze too much electronics in a too small package, which broke stuff.

What it comes down to is that the pcb is a breadboard. The solder kind. and it was connected to the lcd with some wires and a header. This was aparently too fragile, because the lcd broke. 

I am not going to fix it because the speaker still works and the volume control as well. I will just us it as-is from now on. 

So now i know for next time. calculate more space for pcb's and heatsinks and try to use actual pcb's to save space.

Also another thing that i noticed. People on ebay oversell their batteries. Who would have thought. Basically i bought a battery pack described as 4 Ah 12v. My guess however (i didn't measure) is that it is 1 Ah max.