Why does my engine keep cutting out when I release the clutch

I have a 1999 16 hp Craftsman riding Lawnmower. I have already replaced the dead man's switch several times. But I'm still having a problem with the engine cutting off when I release the clutch.

I just replaced the head when a head gasket blew. That seems fine. The engine is running great. But this problem with the engine cutting out is several years old. I've tried replacing the switch several times, I clean the plug with electric spray, I even tried to disable the seat by removing the sleeves and nothing seems to help.

I'd appreciate any assistance with the problem.

Thanks in advance,

Terry