Weird results with OCD build

[rufustf]

I found a sch. and a layout, decided to omit the germanium diode by shorting it/leaving it out & replacing it w/ a wire (didn't want "fuzz", plus my friend with the germaniums is way across town now), and had to sub the 68pF cap for a 42pF. Not too big a deal, right? Anyhow, I played through it at home at low volume through my regular gigging amp, and my DIY champ. Both were great. Then I took it on a gig, and boy, did it behave differently. No matter what I did with the tone control, it was "farting out" all over the place. What I mean by that is that it caused the speaker to act as if I were trying to put too low a note through it. It would sound good for a second, but when I dug in with a stronger attack from the guitar, it was fartin' time.

I am baffled by this.

I also have taken a 1 year+ break from electronics due to, well, life working it's magical mojo of good things and headaches all wrapped into one, so may have dropped the ball on something. My usual build experience is that it either works just right, or not at all. There have been a few exceptions, of course.

Any tip on troubleshooting this is greatly appreciated. I looked through other OCD threads but when the prompt said "are you sure you want to respond? this is old..." I declined.
Thanks in advance-
RTF