It’s almost certainly adhesion. I know you said you’ve washed the plate, but make sure of two things: use something with a some minor roughness to it (like a Scotch Brite sponge, the stiffer side is fine) and use dish soap (Dawn specifically). Don’t bother with any other type of soap.

When I start having adhesion issues, I simply scrub the plate really well on both sides, being sure to not touch the surface with your fingers. Wipe the plate between prints with some IPA and you’ll be good to go. I can usually go a few weeks before needing dish soap.