Though I support Dinosaur boards myself and, owning one, I have looked at it with all the training and expierence I have (Certified Electronics Tech Licenside Ham Radio operator going on half a century,, Just put a 36 year old radio back in service,, complete with a repair or two). and the feeling of QUALITY looking at those boards was amazing, IT IS THERE.. OEM board, (much more expensive) not so well built.
That said: I think you need to look to the high-temp cut off.. 20 seconds is control board, 2 minutes sounds more like high temp cut off.
IF that is the problem, it may be your ducts need to be cleaned out.