I've had this many times with the AM882 and the EM806 and it's a random thing, it's like they must put something in backward...Lol

Regards the Step edge then I'm not so sure because while I've had many drives be on the wrong side of the edge I never actually checked which was at fault, the controller, or the drive. I just do a quick back n forth check with g-code and if it drops steps then flip it over. I do this on every machine regardless if the drive and controller say they match or not.!