Exmark 2blade 48" cut- Exmark brand motor (24hp)

[Scolabird]

The second dealer seemed to have fixed the original problem.
See the original post. He says that he put an additional 150 hours on it after the repair.
Blow up the second picture. Do you see the oil and debris buildup on the cooling fins?

Im no ace tech, so when i ask ?'s it's in the spirit of learning and troubleshooting... so what are you thinking about oil and debris buildup on cooling fins? I only ask as with daily use and living in a dust bowl, probably all 4 of our mowers look about like that? If any ever had spills/leaks we pressure wash but... are you ssying their is some sort of shut down occuring due to a safety "overheat" feature??? Isn't that small heat sink in the photo, a voltage rectifier of some sort? Any help appreciated... again weve resolved simple seat switch failures and things but not certain where to begin as (A) this mower has a few- pto safety, the actual pto clutch, a parking safety, and i think one other safety shutdown and with the issue being so random/ intermittent after hours of use im not sure howntovtest/re create