mechanical thermal switches are 'almost' science, their precision may alter up to 20C error margin, I saw this on heating mechanical thermostats (dunno if this word is in englisk
).
yes, it may be de-calibrated
you may check with some themp meter, but anyway 30C seems toooo low imho, for apliances like this for me 60C-70C is ok
if you live in some countries, 30C may be ambient temp in the summer, whare is the heat margin for the motor, between 30 and 30?
just get him out, test the motor, if it's shorted anyway it will die, watch him spinning for 30 minutes and see how hot it gets