The NTC should reduce with increasing temperature, it needs to much lower than 600ohm to make pin 8 of the comparator (N1236) higher than the 10V reference, we used the heat-shrink gun to warm them to test them at work, a hairdryer should do for checking it, the manual states pin 14 of the comparator will be low at above 80°C.
As the OVP uses another comparator that will work in the same way, increasing voltage will put pin 10 above the 10V reference and trip that one.
If these are SM components measuring any voltages would be tricky, but not impossible, then again if the PSU shuts down before you can measure these it would be difficult to prove if these are causing it.
David