If they are printed off-grain - forget it. I won't use them. Now I check fabrics over carefully before buying panels.
If they are printed on-grain, but the fabric has gotten skewed in processing, I will try to "train" the fabric -
first by machine washing and drying - sometimes that does the trick
if that didn't do it, then I will resort to the old-fashioned method of pulling on the fabric to make it "go the right way" - and then will try to press it down with starch or sizing - much as I prefer not to use starch or sizing