Bug: unit menu glitches when docked on left side

Being an old-school C&C player, I like my unit menu on the left side of the screen (press alt+up when in game to move the unit menu). When docked in this position however, at first everything is fine. Then after a while, I haven't been able to figure out what causes this, the menu starts misbehaving:

first stage

• the menu border is nog longer visible
• unit build icons remain when no unit is selected
• unit build icons are clickable

second stage

• same as first stage, but unit icons are no longer clickable, so the game becomes unplayable

As mentioned above, I have not been able to figure out what causes this. It does not seem to be related to specific keypresses, yet it does not occur out of the blue when no keys are pressed.

Alt+tabbing out of and into the game fixes the menu for a while, but not permanently.

I would really like to be able to play the game with the menu on the left side. This used to work fine a few years back at least.

Menu working properly

Menu not working properly

I'm afraid that there are a lot of issues with the UI once you start rotating it around. It was fully functional in the base game, but it appears that over the years FAF lost support for it. I don't know whether it is trivial to get it fully functional again.

I would be happy to help locate and possibly fix this issue. But I need some help getting up to speed.

• Which repository hosts the code for the UI?
• How would I go about debugging the UI and running my own branch?

As a quick workaround in-game, you can swap the ui back to the bottom and then to the side again.

You get a small visual glitch still but doesn't affect the gameplay - it would be nice to get this resolved however.