It seems that this is still an issue -
Having Prime rewards from Twitch over ~60 from letting them build up breaks Amanda Holliday's inventory, making them all invisible.
This can be seen in: frame drops when viewing her inventory, the Companion App showing her vendor items in full, and IDM doing the same.
This has been a bug for over a year.
Please fix, or at least throw up a site that lets me hit a big red button which claims them to my vault automatically. This is literally just an issue with her ingame UI.
To further prove my point, here's screenshots of the app, DIM, and then the game - items showing in the former two, but not the latter.
https://imgur.com/a/yULUFDa