GE 24 inch Wall Oven / Microwave unit. GE Wall oven self clean fails with F2. The temp probe tests okay per below,

A few years ago a electrical surge took out the oven control board. I Replaced the control board assembly with a NOS unit . Tried a self clean and received a F2 error code. Replaced the temperature sensor twice and that did not fix it. fas forward a couple of years, now I need to fix the self clean instead of manually cleaning (bad knees). Things I have checked:
1. Oven works fine in normal bake and broiled mode.

2. Oven fails on F2 error code 20 minutes into self clean cycle. Oven did get hot enough to burn some of the deposits to ash.

3. There is a fan located between the microwave and oven. It blows air across the top of the ovens outer shell where the lock motor and what appears to be temperature limit sensors (one os a manual reset switch) are located. This fan does turn on during self clean. I cannot verify it is turning fast enough, but there is a very faint breeze coming out of the vents between the microwave and oven. Just enough to barely move a kleenex. There is no dust screen on either side of the fan or in any of the sheet metal channels that directs air flow to it.

4. At room temperature, temperature probe reads 16 ohms (part number WB21X158). When the error occurs the probe is reading 75 ohms. NOTE this is a 16 ohm sensor and is the correct sesnor per many online databases including the GE parts database. However I have seen a pdf of the ovens repais manual that says it should be a 1100 ohm?

5. Visually inspected control board and power transformer board. No signs of damage or overheating, no smell of magical smoke.

6. Inspected and verified all connectors are clean and tight.

7. Left the control board hanging out of the unit (its designed to swing out on a hinge). Placed a 12 inch fan in front of the unit on high, Directing the air over the control board and into the cavity the oven fan blows into.

8. Visually inspected relays on the oven transformer power board. The are not welded and move freely. Some carbonization but no sign of pitting / arching / welding

9. Door lock does work. Front panel blind while;e lock motor is run and then goes solid after the latch goes home. Door will not open until after the unit cools down after about a hour.

Ideas?