since all woven fabrics (if they shrink) will shrink more in one direction than the other it is normal for fabric to be a bit (mis-shaped) after washing/drying. many people who choose to pre=wash pre-cuts find this happening- it can be quite bad with 5" charm squares-
when pre-washing yardage you simply don't notice it as much it is not as big a deal....that's why if you contact the fabric manufacturers and ask they will tell you they do not recommend pre-washing any pre-cuts- they say they are meant to be used as they are- pre=washing is not necessary ...
they simply do not understand that (some of us) always pre-wash- regardless---
so we have to live with the results of our (not-recommended) decision.
one of the big reasons i seldom spend my hard earned $$ on pre-cuts...the frustration (and waste) seems to outweigh the convienience for me....i'd rather cut my own pre-cuts after pre-washing- that way i know my 2 1/2" strips are going to be 2 1/2"...and my fq's are going to be 18"x20"