The temperature problem was tackled first, apparently the machine was triggering the temperature protection unnecesarily so I gathered a general understanding of it's circuit from the schematic (seen above).

 This machine is puerly analog and the fault detection consists on an LM35 IC thermaly coupled with the power stage heatsink, this component outputs a voltage such that:

This is then followed by a Low Pass filter, presumably to filter out high frequency noise and avoid unnecesary triggering. It's output goes into an op.amp in a non inverting configuration with gain 10 which boosts the signal level to:

After the signal is conditioned a final stage sets a threshold for triggering, this is achieved by comparing 8.18V generated by a voltage divider against the signal with an op.amp in a comparator configuration. 

This sets the protection temperature at 81 ºC which after measuring the heatsink temperature to be much lower (with a PT100) proved that the machine was triggering unnecesarily.

The comparators output signal, labeled as THERMAL, drives the gate of a JFET (not pictured) which, upon receiving a high level input, ties the input of the amplifier to ground muting the machine and thus allowing the power stage to cool down avoiding a catastrophic failure. 

After understanding the muting mechanism it was inspected for faults where it was discovered that the ribbon cable carrying the analog temperature signal had been teared (tear not visible on picture), this left the voltage floating at a level equivalent to around 1000 ºC! No wonder the machine was trying to protect itself...

The teared part was cut and resoldered on to the PCB.