Thanks, Peelee! Best Silver Dragon in the world!

I've got a problem with my printer, and I was wondering if the Playground could help.

It's an Anycubic Photon resin printer, and I can't seem to get my prints to stick to the build plate. The first few prints came out fine, well, mostly fine, but lately they end up as a thin film on the bottom of the resin tray. I clean off the build plate (and the resin tray) after each print with isopropyl alcohol, and filter the resin as well. I've replaced the film at the bottom of the resin tray to no avail.

Any suggestions on getting my builds to stick to the plate instead of the tray?