Orange Squeezer suddenly acting goofy

[ayayay!]

...yes, I searched first.   Moving on...

Weird one.  My OS has been working fine since I built it in June.  But suddenly this weekend it got buzzy/distorted when strummed hard.  I reseated the FETs, but it didn't help. 

As I recall when built, the trimpot (10K single turn) only had a narrow range to feasibly work with.  Now the trimpot works pretty much all along most of the rotation of it.  I can definitely hear it rebiasing all the way through the from end to end, but like I said I recall it having a lot less room to play with on it before.

I replaced the 4558 with a TL072 and that helped somewhat, but it still distorts easily. 

Waddya think?  Replace the FETs w/ new ones?  (2n5457s) 

[Philippe]

You might consider replacing the trimpot if there is some slop in the set screw. Some are 'looser' than others & the bias adjustment can shift due to the amount of handling the stompbox gets while setting-up, being moved around etc.

[Tony Forestiere]

Supply voltages? Dead battery?