@youClown Was the headset maybe a little looser before you worked on it? Have your tried backing off the threaded cup a little and seeing if it doesn’t get as stuck?
It could still be useful to eliminate the possibility that the issue was always there, and you just didn’t notice it because the headset wasn’t as tight and allowed a full range of movement without seizing..
100% sure it's not something else causing the stiffness in the steering? i.e. cables pulling? If it's fine in a certain range, I'd also be tempted to ride it and see if anything changes as things bed in.
@youClown Was the headset maybe a little looser before you worked on it? Have your tried backing off the threaded cup a little and seeing if it doesn’t get as stuck?