P-Bass problems

My main instrument is a mid 2000s Cort Sp-Pb that’s been heavily modified with a kickass 2 bridge, 1960s full size American made pots, 1970 fender p bass pickups and a new set of tuners which are phenomenal but unbranded.

But yesterday I was giving the electronics a little bit of a clean up-as I like to do occasionally- and when I finished putting the pickguard back on, I plugged in my bass to my pedalboard and switched on my amp and I hear a awful screeching/buzzing sound that worsened when I touched the tone pot and was almost entirely unnoticable when I touched the strings, tuners, or bridge. So I took off the pickguard and inspected the wiring and...it looked exactly as the wiring did before, I did nothing to make it do this, I looked at the wiring diagram I used to put it all together and the pictures I had of the wiring before and it was exactly the same, not a thing had changed.

I used a bit of electronic cleaner and a small Q-tip to get into the small spaces where I couldn’t get with my other tools (a tooth brush to clean any dirt or dust off of the wiring and a microfiber cloth with electronic cleaner on it) but I made sure that no bits of cotton were left behind. I tested each of the pots individually and together and there was nothing wrong with them, I also tested my cable with a cable tester and there was nothing wrong with it.

I am at a total loss as to what could be causing the problem, it sounds like a grounding issue but I checked that and it is well grounded. The only thing I could think of at this point is maybe an issue with a pedal or my amp.

Any advice would be greatly appreciated.

Here is the wiring diagram I used also.

 

I am entirely unsure of how this got put into the effects super- —thread and I am unsure how to change it