I had a similar prooblem some time ago. It drove me nuts; I'd have a
beautiful gel that would fall apart when I'd separate the plates. The
problem turned out to be that I wasn't letting the gel sit long enough
after pouring. I would pour the gel first thing in the morning, and run
the gel early afternoon. If you're not already doing so, I'd recommend
pouring the gel at the end of the day, and running the gel in the
morning. This seems to give the gel enough time to adhere properly to
the bind-silane coated plate. Good luck.