Just to clarify, the hardware is sound. The cooler on the GPU is working perfectly well. 

However, this is the second time I have had this happen in about a fortnight. 
I power on the machine, log into Windows 10 and as the startup apps begin to load in the background my GPU fan hits the ceiling and the readout in Precision X is telling me 91c which is incidentally the target/max temperature I've set my GPU to for GPU boost (106% power limit and 91c) as I am on water and it will never reach this temperature. 
After rebooting, the GPU is idling at 24c.

Also worth mentioning, at the time this occurred, Corsair Link reported the same temperature. 
Running Percision X OC version 6.0.6 Corsair Link version 4.0.3.154 and Nvidia GPU driver version 375.76

Reporting this as it's one of a few bugs I'm confident are related to Precision X.

Anyone else seeing this at all?