Need help thermionic distortion feedback oscillation problem

[ninemag]

finished a build on a pedalpcb thermionic distortion last nite- sounds good,BUT I'm getting a nasty feedback oscillation when I turn the "tight" knob up more than 20-25%. Starts at a lower pitch and rises as I turn up the knob.I checked the pots w/ my dmm and they are working proper. Changed the trimmer. Looked under magnification and didn't notice anything too obvious. I've built a few pedals, but this one is the most complicated so far. Any ideas or advice would be GREATLY appreciated!
Thanks!

[Willybomb]

There are two fixes to squeal with a BE-OD.  Put a buffer in front of the circuit, either in the enclosure with it, or up the 120p to 1n, 1.5n.  If the buffer doesn't work, increasing the cap does.  I increase the cap as par for the course now.

[ninemag]

Just tried a 1n5 in place of the 120p- made it a bit worse lol. Now I can't get the hum/ squeal to go easy with the tight knob- affects the gain knob now -