had a similiar problem, with a different stainer,doesn't seem to be the stainers, did some checking and found that our xylene needed to be changed more frequently and the slides to cool a bit before deparrafinization, seemed to help the problem, also checked our water bath temps, when they are a little too high(to get rid of wrinkles in biopsies) found the same problem occurring. I tend to think it is a heat problem.
just my two cents worth.  good luck.
                           dana