npn Mangler oscillation

[jalmonsalmon]

 I recently made 2 manglers, one is with germanium and that one works fine, and I made another with BC108s, reversed all the polar caps and diode... wired up it up and seems to have a grounding issue. If you turn your guitar volume to 0 you can hear an oscillation going, really hi pitched weeeooooweeeooo type thing, Turn the guitar vol up and it sort of goes away but you can sort of hear it in the back ground.
It is biased at approx 4.5 volts on the sweet spot; I have 2 other sets of BC108s and tried those out but getting the same result. is there a cap value somewhere I can try out or certain other resistor values that would help?   besides that oscillation, I love the effect I am getting but I suspect if I boost the pedal or add it to the chain with other stuff it can get annoying!
sorry this was wordy but any help out there would be great!!!

thanks

[jalmonsalmon]

Answer to my tech question:
I just realized fuzzes are tempermental beasts.
Plugged the silicon version mangler into another amp in my bedroom and I don't hear that noise at all... Could be all the stuff in the living room where I 1st tried it out. Still strange that the PNP version did not make that noise.
Oh and if yall did not know, plugged  a ThunderPuss mosfet booster in front of the silicon mangler and crank the fuzz... it does serious oscillation there!  Not sure if that is normal, goes away when the fuzz is backed off a bit - does not do that with the other NPN Mangler...  Any insights/advise let me know
(new to fuzzes)  ;-)
Overall, happy with the mangler and will use it in a live setting!
Next build for me will be the Boneyard!

Thanks!