This issue is currently being looked into my myself.
I have managed to seemingly fix the issue -- The issue as it seems currently is a compatibility issue with the ElvUI sub-add-on ProjectAzilroka's section Movable Frames. Disabling Movable Frames, and using BlizzMove or MoveAnything seems to fix the issue inside Garrisons.

I am still testing Order Halls and the BFA Heroic Missions.