I was receiving errors while accessing the promoted controls of each toolbar panel and after some debugging I found that it was happening in any panel that has a control promoted from inside of a dropdown control.
For example, it was throwing an error when I accessed Design(WS)->Solid(Tab)->Create(Panel)->promotedControls with the promoted controls being:
['FusionCreateNewComponentCommand', 'SketchCreate', 'Extrude', 'Revolve', 'SolidLoft', 'FusionHoleCommand', 'MirrorCommand', 'PatternRectangular']
Of those, "PatternRectangular" (Rectangular pattern command under the pattern dropdown ("PatternDropDown")) was the only control not from the toolbarpanels top level. After I removed its promotion, accessing the solid create panel no longer threw an error.
Hope this helps. I think this may be the root cause of some other exceptions while accessing various ui objects, I will look more into it. You can send my employee login info to my email. (Just joking lol but with how well I know fusions ui at this point, I wouldn't be opposed to applying to a position where I find bugs/create sample code if it existed, I quite like this stuff)
