..Wait, you mean the X?
In any-case.. I'd a) check the
cables, connecting the amps to the galvos; ie: when you did your 'amp-swap test', did you disconnect the amp-side only? Or the galvo-side only? I ask, because you should try
both, in case one-cable / connector, has a bad pin
(yes, I've seen cables 'go bad', just 'sitting', for some time.. it's the same voodoo that causes those incurable ground-loops.. jk.. If one of the PD (position-detectors) is not getting back to the amp, that can present like 'spaghetti', like that..
b) If all that checks out, try
(after turning OFF the amps / signal.. see how the (suspected) bad galvo 'feels', when you (gently) grab the mirror by the edges and 'rotate' it back / forth.. Does it feel 'gritty' or 'tight'? It does-seem that some-brands of 'Chivos' lube tends to 'gum-up', after sitting awhile.. Of course, that should rarely, if-
ever, happen in galvos, but.. Whattya expect for $29.95..
..Just a couple quick-thoughts, fwiw..
j