The two identical coatings, one with corona discharge and one without, both started loosening after 5 minutes of processing. Loosening looks very identical in both samples.
Coating thickness doesn't seem to affect much. Thin coating took 1 minute to diffuse thoroughly (darkened from the base side in developer), and thicker took 5 minutes to diffuse, but both started loosening at the same time, after 5 mins.
But what's even more interesting, I made another coating so that I dragged the PET base four times through the coronizer. When I did this, the first time I needed much force to drag, the second time was much easier and the two last times it went through without any force. After this, I could feel the static electricity. BUT! This coating had loosened completely already during drying, which is quite interesting!
Currently I'm giving positive corona discharge (meaning that the corona wire has the positive voltage), side to be coated facing the corona wire. Maybe I should try changing the polarity? Or then again, I could rise the voltage to give stronger corona discharge. I can't even see any glow even in dark now.