Even though we got conscientious support from the supplier we purchased it from through emails from China it was quite an ordeal adding the “self-leveling” sensor. Of course, my friend didn't realize that he would still have to level the huge bed... just not as often. He thought the operation was going to be completely automated. I tried to explain that no piece of glass was that size was going to be completely flat and that we needed the sensor to make up for the imperfections if he wanted good adhesion.
He needs to upgrade to a printer the does auto bed leveling. You use that in conjunction with bed probing, since the four corners may be "level", but that doesn't mean the bed is "flat". The auto bed leveling is nice when you use a different thickness build material, let says switch from glass to a PEI sheet. No screwing around with thumbscrews and a feeler gauge.