Okay so I have a spektrum sr301 that I just bought and it seems to cut off/lag and I did check the LED on the receiver and whenever it does that it turns off. It seems whenever I turn a lot it does that.I put my car on a stand and kept steering and it did it again. could it be that I need a bec? My servo is a HiTec HS 7954SH and my brushless setup is a 1/8 mamba monster combo gen 1

Gen 1 MMM has a low voltage BEC and is not programmable via Castle Link.

Get a capacitor (Spektrum or otherwise) and plug it into the aux channel. Sounds like the servo is drawing too much voltage IMO anyways.

spektrum receiver+ castle ESC bec+ high draw servo= the worst combo for glitching possible. get either a cap for the receiver, or an external bec.

I just got a spektrum receiver cap earlier and works great ! But ...My dx2.0 has bad range !! I can't even let it go far or it totally drops like the car is dead . Idk what to do about that now ...