I’m just putting this here because I only found the answer on the Prusa Forum…hope it helps someone.
I was having real issues with PETG prints failing to stick to the PEI print surface. Anything over about 50mm tall would pop off mid print no matter how big the brim or even with mouse ears built into the model.
Cleaning with isopropyl alcohol did not help.
Washing the build plate in very hot water and dish soap fixed it. It also seems that swapping from PLA to PETG will cause issues for the PETG adhesion so from now on one side is for PETG only and the other for PLA.
Probably not news to most but after years of PETG tearing up build-tack this was the first time I have ever had adhesion issues and it took way to long to find the answer.