[Ashlandchris]

As I said, this is beyond my absolute knowledge, but there is clearly something causing the ESC to cut briefly. That will either be the thermal cut out or the voltage cut out I'd imagine. If you have checked the thermal is Ok and that doesn't solve it then a capacitor may help - I'd imagine that on the straight there is the highest power draw so that might cause a dip in voltage momentarily which is cutting the ESC. As soon as voltage levels it comes back on. My understanding of a power cap is that it evens out the power draw so could eliminate this?
Also, what servo are you using? I've heard it said (but not sure exactly what it means) that some such as Savox are "power hungry" so if the straight is the peak power pull, followed by the kick in of the servo, those 2 things may combine. But as I said, this is pure speculation as I don't know and am just summising.
This is just a thought, but could you try a telemetry module with your receiver to log voltage? Is that what telemetry will do - it may show if it is a power dip causing the problem?

All I know is that on the 2 occasions I've seen the same, the thermal cut out solved one and the 2nd was solved by the driver who swapped his esc for a spare - so easily could have been an incorrect setting?