Could you check your model number.
GEW925)PWO does not come up but GEW9250PW0 does.

I just want to be sure that we are looking at the same thing.

I am assuming that just the heat drops out.

Do you have the tech sheet for the unit?

When the heater shuts off if you restart it right away does it come on for another 15 seconds or do you have to wait before restarting to get heat?

Have you tried different cycle types and heat settings to see if it does the same thing?

Try different heat settings.

If it is a problem with a connection etc. opening when it gets hot then odds are high that by the time you get to check it the ubnit has cooled down enough to reconnect the fault.

Perhaps it would be possible for you to attach meter leads either taped on or with the use of clips across the heater relay contacts at the control board so you can monitor it.

When the heater is on it should be 0 volts.
If it stays at 0 volts when the heater shuts off then you know the problem is in the circuit from the Heater Rtn side to the L2 line.

If it jumps to 240 then you know the relay is opening and it is either the board or the thermistor.

Check the thermistor with a meter.
Check the connections at the heater relay contacts and the thermistor connector for a bad joint.
Cold solder joints are often a duller silver color and/or may have pin holes.
While watching the solder side of the board gently wiggle the components to see if the component leg moves in the solder.
A magnifying glass comes in handy here if you have old eyes like me.

I replaced the thermistor and at last report it was working