Eric, You're welcome. Tell me tho, you did back them off ~2 turns after bottoming them? Need to do this to get some 'room to move' the mirror cell.
The reason for the screws not being turned equally, is simply a cell design/manufacturing tolerance issue. Nothing is perfect.
Glad to be of assistance.
Regards, L.
ps. Oh, it helps if you collimate in the daytime too. Can see things clearer. Just point the tube towards an open door or window.(Nice even light source).