My parents dryer only works when the Start button is held down. After googling, I was told to swap out the relays to see if it's the motor relay that was broken. I swapped out the relays and it worked, but the heat also worked so I left it at that. This was about 4 months ago and now the same problem is happening.

Do you think I need to get 2 new relays? Or is there another problem?

Thanks I'll try that and report the results back. It's at my parent's house so I won't be able to get there until the weekend.

What is the model number?

Do you now have both drum rotation and heat?

The reason I want the model number is that what is happening is a very weird problem and perhaps a look at the tech sheet (if I can find one) will help explain it.

The relays must be OK as they work, at least I am fairly certain they are OK.
You get the exact same problem even though the original heater relay is now the motor relay.
It could be that it is a control board problem.

Did you ever just unplug the machine for a couple minutes without doing anything else?
The reason for asking is that if the control board is hanging up unplugging the unit would reset the board.
My thinking here is that perhaps swapping the relays did not fix it but unplugging the unit while doing this did.