We started drying our ER/PR slides in a 80 degree oven for 30 minutes.  We
first got wind of this through the Ventana support group.  We've been doing
antigen retrieval in a microwave pressure cooker, for no more than 30 minutes,
usually 10 mininute when up to pressure, which usually takes 10 minutes.
Sometimes we have problems with sections falling off.   After all this, it's a
wonder they stay on at all.
Anyway, my guess, the problem of falling off, is due to the tissue, ie. too
much fat, under fixation and any other excuse that takes the blame off of us
fantastic histotechs.  Hope my two cents worth, helps.