I have noticed that when I go thru a long rythm section , thottle on , throttle off multiple times , the power starts to cut out to the car until I let it catch up and then it fine. What would cause this issue. I ran into the same issue with a different brand esc so I dont know if thats the issue. Radio maybe? Using the sanwa mxV.
What ESC's have you used?
It could be multiple things. First I would check the sensor wire by replacing it with a new one as that can cause intermittent power issues if it's going bad or gets jostled too much. It could just be coming loose ever so slightly going over the rhythm sections.
It could also be the electronics combo used. If the ESC can only do 6v or less and you are using a servo like the Savox line, that could be causing brownouts when the load is too high for the BEC to handle. That's usually resolved by adding a Glitch Buster.
There is a chance it is the radio but it's pretty unusual for a Sanwa radio to respond like that. It's generally one of the other electronic bits that cause issues. But if you have a different radio to try you can at least rule that out.