Odd electronics behavior, delayed throttle & steering response

[WheelMan]

After scouring the web for examples of people having similar issues to mine, with no luck, I've come here in hope's for an answer (or at least some guidance).

I've been running a system consisting of an MM2 with a 1717 Motor, 10 amp Castle BEC, and a Flysky GT3C radio, on 4S for quite some time now, with zero issues. Everything operates flawlessly. But the second I plug 6S into this setup, I get weird delayed responses to throttle and steering inputs. I can go back to 4S and everything is fine.

I have the same issue with another vehicle that has the exact same system configuration, only exception being an XL2 instead of the MM2 ESC. Runs flawlessly on 4S, but the second I plug 6S in, I get the delayed responses.

Any idea as to where I might be getting this issue from? Everything is soldered up very nicely (I'm a bit OCD about that), so I know I don't have any shorts anywhere (plus, I'm getting the same symptoms on two different vehicles).

To explain the symptoms in more detail, I'm getting very "glitchy" steering response. If I turn the wheels left to right quickly, the servo moves very erratically, and stops momentarily in random spots and then seems to "catch up" and complete the action received by my input from the transmitter. Throttle is doing something similar. At times I will pull the trigger and let go quickly, as if to apply a small burst of power and then let off, but nothing happens until after I've already completed the input on the transmitter. I'll pull the trigger and let off quick, then a moment later, the vehicle will burst forward, as if there was a time delay between my input and the vehicles receipt of that input. I should add that this is very inconsistent behavior though. It does not happen all the time. Sometimes it will operate as if nothing is wrong and then all the sudden it will catch me off guard and act up again. Which can be very irritating. For example, yesterday I had one of the vehicles out on 6S, and I was experiencing situations where the system was acting as if I was holding the throttle at 100% for a few seconds straight, when all I actually did was "goose" it. This resulted in a few nasty crashes...as I'm sure we can all certainly understand, as a 1717 motor on 6S can be pretty wild!

Anyways, I'm hoping someone here can shed some light on my issue for me. Or at least point me in the right direction. I thought for sure I would find posts somewhere online from people experiencing these symptoms, but I came up short. So thanks in advance to anyone who can help!

-Travis