This looks like a typical reaction due to an antibody against a low frequency antigen (like anti-Dia). This is how they are usually found. If you have the ability, I would run a selected cell panel on the pre and post using panel cells that are positive for Dia, co, V, LuA, KpA, etc. If not, send it to your reference lab to identify the antibody against the low frequency antigen. In the meantime, as you have already done, all xm's should be AHG.