Reply by Aj2

It doesn’t take much to throw off the alignment on a newer style dovetail jointer. Esp if it’s used & some handling of the jointer from the ends of the tables will do it.
Might just need cleaning of the ways you want any dirt of wood chips in there. Keep that in mind if properly tightened gibs doesn’t do it.
Shims are very last resort.

Good Luck

-- Aj