Samsung gas Dryer Dv365gtbgwr/a3

[Turbo1002]

New here and want to say hello and thank you for reading my post.  My problem has been on going for a year now.  The dryer will continue to tumble on cooldown showing 1 minute on the screen for hours without turning off.  The dryer does turn the heat off and it will stop if you open the door or push the power button. After replacing the main PCB board the problem was resolved only for a few months, then it comes back.  Over the past year I have gone thru two used ebay boards and two brand new Samsung boards. That's a total of 5 PCB boards including the original which was in the machine for over 10 years without a problem.  I have also changed the motor thinking that was causing the board to go bad.  The thermistor was also replaced. The machine was torn down and cleaned thoroughly of all lint.  I have found this diagram on the internet which I believe is very close to my machine except mine is gas not electric. Also, here is a picture of my original board.  Here are my questions please

1.  What can cause 5 PCB boards to go bad and cause this problem? Can they all be defective?

2. What part on the PCB is going bad? 

 

[Turbo1002]

Found the exact diagram for my machine.