I'll add that if I understood the OP's data need/question all the answers are already in hand, the actual fork. Does it look/measure as the same as the old one?

Headsets want a certain shape to interface with the fork crown. Some forks have this shape molded into them, it was common to not do this and instead have a removeable piece (fork crown race seat) that gets transferred to the new (and needing it) replacement fork. It sounds like the OP has one of each... A lack of proper bearing/frame interface certainly might cause wobbling about, but there's a bunch of other possibilities that can cause a poor fit up. But with the poor description/lack of visuals I really can't say what's going on. Andy.