I’d suggest the less-likely bias/temp issue but yours is an Si unit. The only other thing I would suggest is if you can switch between amps and input levels.
I have the Boss TB-2W, which you would think is the Jelly to the PB of my 1959 RR. Strangely when playing the amp at volume, the TB only does one oversaturated tone regardless of where the TB’s knobs point. It does clean up well rolling back the guitar’s volume, but I just get this one saturated (albeit usable) sound. If I turn the amp’s volume to near-nothing I suddenly get that thinner buzzier fuzz that I was shooting for, but the volume is not necessarily where I want the amp.
Drop the pedal in front of the lo sensitivity of my 2203 JMP like billy corrigan did w his muff and BAM, exactly what I want with room on the dials to add or subtract. Fuzz is a weird bastard. It is temperamental with pedal order, with anything you stack, with the amp, and even with pups.
Maybe it's just me, but I find that the fuzz face reacts very differently with different rig chains, guitars, and amps. It seems to me to be low volume. I think you might have to get the volume a way up to hear the fuzz at lower settings. Guitar volume knob rolling appears to be the way to reduce mud, not actually dialing the fuzz back.