Double-hung sash drifting sideways: balance, pivot shoe, or frame issue?

My double-hung sash has started moving sideways as I raise and lower it. One side drops slightly and rubs the jamb, while the opposite side has more clearance. It still operates, but the movement feels uneven rather than simply too heavy or unable to stay open.

Before I remove the sash, I’m trying to narrow down the likely fault. The sash hasn’t been intentionally removed or tilted recently, so I’m wondering whether this points more toward:

- a disconnected or damaged balance cord
- a worn or shifted pivot shoe
- a broken guide or track component
- the frame being out of square

I can inspect the jambs with the sash closed, but I don’t want to tilt it unnecessarily if the balance is still supporting it. Are there safe checks that distinguish a balance problem from a pivot shoe or guide problem? For example, should both balance cords remain equally tensioned when the sash is raised slightly, and would a loose shoe usually be visible with the sash still installed?

If one side’s cord or shoe is visibly loose, broken, or out of position, is replacing that hardware generally a reasonable repair, or is sash removal usually unavoidable?