You indicated in your post, that they have more than one projector. And you seem to indicate, that more than one (if not all) are doing this shutdown.

It would be near impossible to get brand new projectors, that were all defective. Then again, who knows where they purchased them from.
Assuming the projectors are good, this would point me towards those menu settings for auto shutoff (even if the default should have been no).

If the LEDs on the projector indicate it is shutting down from heat (as mentioned above), are the projectors mounted near HVAC vents. It's winter, heat is turned on.