On the X-ONE if still using the blue sheet on the bed. Try increasing your first layer height. PETG doesn't like a squish and the blue sheet is like super glue!. I can run 120% first layer with PLA on that stuff and get good adhesion.
Glass is a good choice but the X-ONE doesn't have any "conventional" way to hold the glass. I have some printed clips that work pretty good. I am also getting ready to try another method and see how it goes.

Another thing people do when using PETG on PEI bed is talcum powder or glue stick. Do a google search on these to get info.