Maybe the splines were not aligned, or the pseudo snap ring doesn't allow it. if that snap ring got bent or out of shape, that might do it I believe. And in order to take out the half shaft, there is lots to undo. But maybe try to take out the wheel, let the air out from the air spring, so there is no tension and less weight, and try it that way. It might allow even to pull it out further, so you can see if the snap ring is damaged.

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Stable: e92is, e46 M54B25, e83 N52, e53 N62 - sold, e39 M54B30 R.I.P.