Is it only with one or with all guitars?
Can you put examples? What guitar and pickup do you use? Active or Passive pickups? Neck or bridge pickup or on both?
What string gauge is in use? The thicker the strings, the more energy / dynamic they send to the PU, by this higher output volume.
Might it be that the distance between pickup and strings is too low so that you are getting unusual high peaks?
Which is not good, because on the one hand the strings lead to higher peak output but are being caught by the magnets of the PU and cannot vibrate properly and thus less sustain.
For my Gibson Les Paul (which is perfectly adjusted by a true artist in his field) with 59' Classic PUs
the distance between the PU cover and the lower edge of the string,
measured at the side of PU towards the fingerboard and for a 009-042 string gauge, is:
Neck PU Bridge PU
high e-string 4 mm 3 mm
deep E-string 4 mm 3 mm
Do you know somebody with an UFX, UFX II, UFX+, UFX III? If yes try and compare whether there is a difference.
Reason: I am using the instr inputs for different guitars with passive pickups
Single Coil: Texas Special. Humbucker: Gibson 59 Classic.
The Gain settings is perfect at 20-22 depending on whether you have Humbucker or Single Coil (+2 dB Gain more).
Gain range is 8-50.
> P.S. Clipping is audible.
Watch the peaks, it will clip if the peaks exceed 0dB on the Instr input.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14