Reverb bleed at 0 on RVB pot on a '65 blackpanel Fender Vibrolux

[Sansteeth]

Hello everyone,
I'm working on this beautiful blackpanel Fender Vibrolux (unfortunately all transformers have been changed and while no "mods"were made, lots of parts are not original inside).
It came in because the customer was complaining he could still hear the reverb when the reverb pot was turned all the way down.
However, I found out the original reverb pot was only going down to 700ohms and the 220k CC resistor to ground coming after that was measuring 272k (RVB recovery stage grid leak resistor).
I changed them both, now I get a solid connection from the wiper to ground when it's turned all the way down and yet I am still getting reverb bleed. It's subtle, but it's there. The footswitch gets rid of the bleed but I don't understand why the pot cannot put the reverb signal to ground all the same and get the same result.
If I lift one leg of the 500pF at the input of the reverb circuit to feed it a signal and look for it on the other side (without the dry signal), I need to crank up the resolution and my scope (analog) gets too hashy on the other side to find where the bleed happens on the circuit unfortunately.
I've had cases of conductive boards on Fender amps lately but mostly silverpanels, but now I'm paranoid the reverb pot works fine, but somehow the grid of the recovery stage picks up the wet signal somewhere on the board.
Have you folks had experience with Fender blackpanels where you just can't fully dial off the little bit of reverb tail left without the footswitch?
Thanks a lot for your input!

[sluckey]

This sounds like a non-issue to me. Teach the customer how to use the footswitch.

Connect a gator clip lead between chassis and the wiper of the reverb pot. Does this kill the reverb?

Also replace the 25µF cap that connects to pins 3 and 8 of V4.

[Sansteeth]

Thank you sluckey for taking the time to help me!

This sounds like a non-issue to me. Teach the customer how to use the footswitch.

  you are not wrong

Connect a gator clip lead between chassis and the wiper of the reverb pot. Does this kill the reverb?

Nope, which makes me think it's happening somewhere else....

Also replace the 25µF cap that connects to pins 3 and 8 of V4.

That also doesn't kill the reverb 

[pdf64]

Have the HT decoupling caps been replaced recently, especially the D node that supplies the preamp?

[Sansteeth]

Hello pdf64, thanks for chipping in!

Not by me but they have been changed by F+T caps not long ago it seems, 22uF instead of 16uF but I doubt that would be the problem.
You think the wet signal could have bled through this way?