Mamba Max Overheating at idle

I've got a Mamba Max ESC that I purchased about three years ago so the warranty is long past up. This ESC has been very good to me and has seen use in at least half a dozen RCs. Recently I noticed though it starts to get hot even when sitting at idle before being driven After about a minute the ESC is very hot and the motor cogs up extremely badly if I try to drive it. I'm guessing somewhere along the lines something got damaged inside.

Does anyone have any suggestions? I've already tried updating the firmware, and it's hard to justify the $50 repair charge plus shipping to and from Canada.