Just wanted to share in case others struggle with the same. Apparently isopropyl alcohol can permeate through PEI and compromise the adhesive holding it to the glass…. I definitely just soak a towel in the stuff straight out of the bottle to clean the bed, and the other day about a third of the sheet just lifted off when I was heating it up, so it needs to get replaced.The solution, according to Lulzbot support, is to use a solution of 90% water and 10% alcohol when cleaning your print bed.The more you know! http://ift.tt/2dH5IFG