It was next to impossible to identify the exact point of failure on the mainboard.

After further tests I know it is not the sim socket.

Evidence suggests it is the NMP #4377210 DBB - Digital Baseband Processor

I am unable to fix this myself I imagine it would require something like a BGA rework station.

My latest more permanent temporary fix was to place a cut down sim the same size as a nano sim on top of the 4377210 and replace the venilated shield.

I have not noticed any increase in temperature and it is now working fine and seems to be holding it's own.