E39 Dynavin N6 + aftermarket speakers intermittent issues+ RPM Whine

[bluewhale]

I know I know what a mess of a title haha.

Hi everyone, I'm having an issue with my speakers that's driving me nuts.
Firstly, my front left speaker works when I set the balance so that it plays, but when I center the balance it sounds much quieter than the others.
One of my rear right speakers will also cut in or out, if i turn the volume up to 75-80% the speaker will work, turn it down to 30-50% and drive for a few mins and it cuts off, turn it back up and rinse and repeat.
some speakers also seem to cut off and on when hitting a curb or bump in road, which leads me to believe a lose connection somewhere, amp over right rear tire looks mostly ok, I'll update with pictures of wiring that an install tech did a few years back. lastly the RPM whine, when I accelerate, there's a subtle whine that increases with throttle input. Almost sounds like a speaker-driven turbo.

to summarize:
-increase volume = all speakers work including rear speaker , low volume =all speakers work, rear speaker doesnnt work
-low volume at front left all the time
-rpm whine increase

I'll upload pictures in about 10 mins from posting, thanks for the help!

[bluewhale]

20200306_142215.jpg20200306_142158.jpgSorry for the poor pictures this is my first time uploading to the site, In the first one you can see a large black wire underneath a screw on the chassis, thats the grounding wire for the amp.
It should be in the lower right quadrant of the photo. Thanks!

Edit: I've also pulled lightly on each crimp, screw nut, and reseated each audio cable in the amp and those boxes (P.S. the R/F I'm guessing is front and rear but what do they do and should i electric tape that shitty splice?)

[MarcoZandrini]

I’m not much of a fan of crimp connectors. Why? They doesn’t always provide a proper connection. The professional way to connect wires is to solder them, cover the soldered joint with shrink tubing and then use heat to shrink the tubing tightly around the joint. Your local Home Depot or Lowe’s should have what you need.