Phase-alignment student seeking Obi Wan Kanshowmi

[LoopMastering]

That reference is probably giving you the most useful lesson here: the correlometer isn't a score to maximize. It is a warning light. A brief negative reading can be totally fine if the mix still sounds balanced in mono.

I'd stop trying to make the meter sit still. Toggle mono and listen for a specific loss: does a guitar vanish, does the vocal move back, does the low end change a lot? If nothing important collapses, there may be no problem to fix. If something does, trace that element back to its track or widening effect and adjust it there.

For the acoustic guitars, keep the body if it sounds good. Don't high-pass the sides just to satisfy the meter. Compare at matched volume, check mono occasionally, and let the sound make the final decision.