I can’t imagine any electronic reason why so it must be a physical thing…you must have damaged the microphone somehow.
You may have gotten the microphone wet from condensation (coming in from the cold into a warm humid house) or, spilled beer or something on it.
Or it is remotely possible that extremely high sound pressure levels could have damaged the microphone element. But they are really very robust, especially the little tiny ones, since there’s not a whole lotta mass to get banging back and forth.
BTW I use my Clip as a guitar “riff recorder” too, and haven’t noticed any degradation of the sound, but it’s usually on an acoustic or “family friendly” amped levels…
My current stable of axes, just for conversation:
80’s Tama 6-string acoustic. Amazing sound and action.
90’s Alvarez 12-string acoustic, rescued after years of overstringing and damp storage
2005 (?) Johnson “Del Sol” tele copy, tweaked and hot rodded to SHS PU config and a Washburn Wonderbar trem. Project guitar.
1965 Gibson SG Special, P-90s (totally gennie). Love it.