Card Icons can't be added/ updated/ removed properly

New user here.
Deployed Mattermost on dedicated server (Esxi VM)

While adding a new CARD on BOARD, Icons aren’t working properly.
Only RANDOM icon is affected when clicking several times on the “random” button.
Selecting a particular icon from available ones isn’t working.

Steps to reproduce
Not sure if this issue is easy to reproduce or if other users met this issue.
Search through Discussion forum didn’t yield any result.

Expected behavior
Icons should update correctly in a snappy way…

Observed behavior
From Console, an Error 500 appear each time we want to add/update icon.

If anyone could shed a light on why this is happening, I’d be greatly thankful.

Link to VIDEO

Feel free to open an issue at Issues · mattermost/focalboard · GitHub.