Sounds like you might have already found my post on this from 2018 - if not I’ve copied and pasted the link below, as there is a lot in there about unusual side effects I experienced on humira including balance. I had been on it successfully for over 3 years before any of those symptoms started - I’d do things like get up in the night to go to the toilet and despite being able to see the doorway clearly I’d walk into the wall. Balance though was one of the last in a whole constellation of symptoms indicating a problem.
Doesn’t sound like you have lots of other symptoms though, so maybe it is isolated to a balance problem?
Have you had vertigo before? Is it possibly linked to that? That can be an easy fix with the
Epley Maneuver - if you have trouble performing it yourself from YouTube instructions, you can see a physiotherapist to help.
Hope you get it solved soon, and sounds like it is time to move on from Humira anyway, glad you’ve been able to get your appointment moved up.
https://discussion.livingwithpsoriaticarthritis.org/t/humira-and-possible-rare-side-effects/8851