As I'm so far aware, this is pretty much global for every user. I believe there is not rlly any exact "fix" to get rid of the issue.

But I can SUGGEST, probably is to just close roblox every time you leave a game, and reopen it. Though it might seem unnecessary, It've gotten rid of the hassle of having to see that the UI is missing for me. Though take my suggestion with a grain of salt, there might probably be a real fix that I'm not aware of.