One you get a piston out, any short rings will be obvious. The ring side clearance (between ring and groove) is normally in the .004"-.006" range; you insert a feeler gauge between the groove and ring to measure this. With rings that are 1/64" short, the ring side clearance will be .019" or more; .010-015" side clearance is what you will find in a worn engine'e pistons/rings. With excess side clearance, the rings will twist up and down in the bore, round the ring faces, etc.
If this turns out to be the situation, then check the grooves in the pistons for being worn/damaged. You should check them with a new-thickness ring to see if the grooves have been worn/damaged too wide to meet new rings side clearance specs. If the grooves worn/damaged, then you will be back to a similar situation. Either replace the pistons, or see if there is a shop locally that can widen the piston grooves enough to use what is know as a ring spacer, or use wider rings if available. Re-grooving and using spacers an old-time method to salvage used pistons; not sure how well it would work with KB's, or if it is really cost-effective here.
IMHO, if there is no ridge in the cylinders, then you might get away with a fresh cylinder hone. But what appear to be shallow radial grooves around the bore in the above pix, is concerning... if they are real, and remain after a light hone, then that is not going to do new rings any good; ring wear will likely be more rapid than normal.
