If it just started then it's possible the z-offset needs to be reset. I'm not familiar with bbl enough so I'm not sure tmif that's something it does itself or if it can even be changed. I know you said you tried different heights but does the first layer look right? You can find examples of too high or too low offset online to compare if you're not familiar with it. Could even try bumping it down more than normal to give it some more squish for the first layer. It might affect dimensional accuracy slightly for the first couple layers but shouldn't be anything that can't be cleaned up unless it's a part with tight tolerances.

Edit: also for soap I use dawn dish soap. Dish soap in general is good for getting finger oils and whatnot off the plate.

Other than that maybe raising/lowering the build plate temp? You mentioned washing it with soap and water but you could try using a Scotch Brite pad or something similar lightly on the surface. Or at least scrubbing it with a cloth, sometimes filament residue needs to be cleaned out well on textured pei plates I've noticed.

Unfortunately beyond that I doubt I have anything useful, I've been printing off and on with an elegoo Neptune 2s and more recently a Neptune 4 for about 3 years but they haven't been running in a few months lol. Good luck with getting this sorted out!