Busted XLR and jack *strongly* hint at amp falling nose down *hard* with some cables plugged in.
Since those parts are usually mounted straight on PCB, they transmit impact and PCB cracks, breaking some tracks open.
I bet strong bemch light and reading glasses or jeweler´s loupe will help you find one or more cracks, specially near said connectors but also near other controls.
Board may "give" a little at the connector but crack a couple inches away, where board moves but, say, a pot or jack does not.
Patience and eagle sight are your friends
And a little bit luck
A Schematic always helps but you don´t *really* need one.
I bet bthe OpAmp with DC voltage on its output is not bad by itself (so replacing it cures nothing) but some tracks around it are cracked, for example an open input (not referenced to ground) can make an Op Amp drift/float to some random voltage.
Or an open feedback path usually slams output against some rail.