As someone that works in a small blood collection facility, my first thought was how did this get through testing. Then I realized the problem is probably related to the antigens, not an antibody. First thing we check is DAT of the unit, which is negative. Then we would test against a couple of random samples from each compatible blood type, which you did. Then I would do a more elaborate ABO, which if there was a problem should have (in theory) been caught during testing. Then I thought about your reactions, 4+ tube, 2+ Gel, that's backwards from "normal" reactivity. Here we see a difference