Yes it has a BEC. Could it be going bad, no way to check, that I know of anyway. Personally I would try a different servo, if you don't have one borrow one from a buddy or another guy at the track. Some of today's high power servos (Savox are a big one) have a reputation for causing "brown out". You could try running a cap/glitch buster as well.

just trying to give you options to try before going through the hassle of sending it in.