Running your Keyence at a low frequency (stock setting) should keep it cooler then a high frequency (mod setting). Did you have the heat sink installed on the esc?
Running a 6 turn motor on a tight carpet track will be brutal on any esc. All top of the line esc's seem to really struggle with the abuse they receive from low turn motors. This has been my experience anyway. I cooked my Keyence zero V extreme using an 8 turn an 12.5kHz frquency.