I've been trying to add to inventory all night. I was looking the forums for anyone else with this issue but I noticed this. So as of 20:44 March 3rd the year of our Lord 2020 the issue is still outstanding.
I can second this, I also noticed issues trying to add cards to my inventory. I get an error message after trying to edit inventory values in the tooltip/pop-up boxes + the changes do not appear, but when I refresh the page the values/edits appear correctly.