fuzz face squeals at high fuzz level

I just finished building a silicon fuzz face with BC108s. When I turn the fuzz all the way up, it squeals like crazy. I have to back off the fuzz a bit and it goes away - like just tiny turn.

Is this normal for a fuzz face or do I have a problem somewhere?

I am building the negative ground version. I have installed the electrolytic caps "backwards" for negative ground.

I am using a Cioks power supply that's outputting just over 9 V. I have also tried using a battery with voltage just over 9 V as well. I re-bias every time when switch power options.

I am plugging my guitar into the FF and then into my amp - no other pedals or anything.

I have biased my Q2 to 4.5 V

I am using a pcb I got from tayda.

https://www.taydakits.com/instructions/fuzz-face/pages/designators-and-components--26

I've noticed something odd while messing around... when I put my finger across both transistors (top of the can), the squeal completely goes away. It was suggested to me on FB that I try putting a 47 pF cap across Q2 base and collector. I don't happen to have a 47 pF on hand but I do have a 68 pF. I tacked the cap into place for testing. It made no difference adding that cap.
I also tried soldering the same capacitor to the tops of the transistor cans like a bridge (like what my finger was doing). Then I tried using a jumper wire to do the same thing connecting the tops of the transistors. That also made zero difference.

The only thing I changed from the instructions was to use a 1KC for fuzz pot instead of 1KB

Hi...The first Fluff Confront employments germanium PNP transistors (AC128 or NKT275); You ought to utilize a moo pick up for Q1 (β=70-80) and a tall pick up for Q2 (β=110-130). Germanium transistors tend to have spillage current and a changing pick up esteem. For the PNP silicon form, you'll utilize 2N3906. For NPN silicon adaptation you'll be able utilize 2N3904, BC108 or BC109. You'll utilize attachments and attempt diverse transistor combinations. To utilize to the negative ground adaptation (NPN transistors): alter to NPN transistors, flip the extremity of the electrolytic capacitors (C1, C2 and C4) and interface the +9V where it is stamped -9V.