John,
What wrong with the unit? I've seen a lot of the SMW units that will not bake because the fan will not run during bake. The K8 relay gets power from the stalled fan relay, which will only send power out when the fan is on.

If this is the case, the problem is still in the relay board, but is not the K8 relay. Rather, it's a software issue that not allowing the fan to run only in bake and convection bake. If this is the problem, have the board rebuild. After you reinstall the board, locate the wire that runs from the black side of the terminal block to the microwave fuse. Take this wire from the black side and move it to the red side. I've heard that the microwave may be sending something down this wire into the relay board scrambling the program.

KC