I have this exact same issue, except I am horde and haven’t found a way to travel back to Uldum. I need to get the “Thunder on the Sands” quest and a way to travel to Uldum (the correct phase of Uldum as I believe the bug where we where constantly falling was due to being in BFA Uldum).
One thing to mention, to all the people I saw in the bugged Uldum phase, all were doing the Windwalker weapon quest chain as their second or third weapon.