My name is Peter. I am a retired field service appliance technician.
Your unit has so many electrical controls and components. In the future remember simple is better and more reliable.
First, your control boards. You have two control boards in your unit. In this case you should have a surge protector for all of your appliances with control boards. You can purchase a single socket surge protector for about $25.00 USD.
When you changed out the one board did you ground yourself by touching something that is bare metal? Static electricity will knock out a control board. You may have a power supply problem where the slightest change may knock out a board. This is why a surge protector is critical.
I had one customer that I had to replace the main control board 3 times in 18 months.
Ok, lets assume the boards are good and you have no shorts.
Lets check the oven wall thermal switch.
This switch is in the upper right corner of your oven back wall.
Disconnect the two leads to the switch. With your multi-meter, set it to the lowest Ohms (Omega Symbol). While depressing the red button, place one meter lead on one contact and the other meter lead on the other contact. You should get a reading of "0" Ohms if the switch is good, otherwise it is bad.
You have two separate motors. These motors may be locked in to continuous run.
On this motor, located under the top cover, under a small removable plate. It has a black contact switch. Remove the two electrical contactors. Using your multi-meter as described above, hold in the contact button. Your Ohms should be "0". The metal contacts may be fused.
This is located in the upper back section of you unit. It has a transformer. disconnect the two wire leads and Ohm them out to "0".
Remember, You still may have a control board problem. Ground yourself and check for burn marks or melted connections.