Tranny problem electrical related?

[hydrastas]

Alright the past few months i've owned my car and put 5k miles on it i've always had an issue with the transmission and getting it to go into R and D. Altogether the tranny has 6kish miles on it since it was last completely rebuilt. I've tried changing the fluid twice now to no luck. The main problem is that when i think i've got the issue cornered, it doesn't stick. Like once i thought it was the shifter cable cause the red mark on the gear select would be halfway between D and N, so i'd wiggle it around and sometimes it would instantly cause it to engage gears, but not every time... another issue i thought it was the ignition switch due to me turning the car off and moving the key back and forth would cause it to go into gear, but once again not every time. One thing i've noticed lately is that the radio's power output cuts into around 1/4 of total output from time to time and sounds like static then pops back to normal and i've noticed that this going back to normal occurs half the time when i step on the brakes hard or on the throttle. So my final conclusion is that one or more of the what seems like thousands of wires in the car is grounding out or something and the movement causes it to unground. Could this have anything to do with the transmission's electrical components? or would these two things not have anything to do with each other?