Yes Phil is correct. Its your TX going past the failsafe limits on the ESC. I am guessing you are using a spectrum? Was both turning and forward/reverse rates limited to 50%?

What happens is that when you do mixing you get 100% on the channels when you go fully forward/backward, 100% on them when you got left/right and 125% ish when you got fully forward and to the right. (or back/left, forward/left, etc) So this can cause the ESC to failsafe if you are near these limits.

I am guessing you only limited one of the rates to 50% (prolly forward/reverse) and the other to 100% so you were still getting 100%+ in the corners.

I am also guessing this was on a spektrum radio. As this has been an issue in the past for some people but can be fixed by messing with the endpoints and rates.

I am working on a programming box to allow you to setup your ESC with the configuration you desire, this means, the endpoints, expo or linear power curves, temperature limiting, deadzone, slew rates, and a few other features. If this was my real job I would have it done by now but unfortunately its not so yeh will have to wait for that one. In the mean time this problem can be solved by reprogramming your TX.

Steve