PEI build plates

[Bikeracer2020]

I've been using the same rough side PEI sheet for two years now and have just done the following.....

Check bed level.
Clean bed with IPA on a paper towel.

Print five or more 50mm square files at various positions round the bed at one layer thickness of 0.2mm.
Print first five at zero 'Z' offset.
Print next five at an increase of 0.05mm 'Z' offset.
After each print remove and see how well the extruded filament sticks to the adjacent filament by holding it up to the light. Try adjusting plus or minus by 0.01 increments.
If the surface is ploughing up and making waves the nozzle is too close.

Edit.....the 'Z' offset setting is in the slicer.