2003 Ezgo 36V forward died and reverse took over

I was playing hole 2 tonight. Going full speed toward my tee shot when I felt a lurch, the cart started braking and came to a stop. When I pressed back down on the accelerator, it would only go in reverse (FNR switch still in F). Drove back home in reverse and speed seemed to go up and down.

I'm looking for ideas.......

It is 100 degrees and dry here today. Played last weekend with no problems and batteries are less than a year old and well taken care of.