@dave Alright! Repro’ed it on new laptop.
I ruled out all the drivers and razer software possibilities. Moved onto windows mouse settings. The bug is reproduceable when your windows primary button is set to Right.
With that setting, I can repro easily by holding down a mouse button while exiting the menu. Set it back to Left, the bug is gone. You can alt tab out to change the setting, no need to restart Boundless.
Works on both my desktop and my laptop. But I couldn’t get it to work with the trackpad. It had to be a mouse.
I’ve remapped my setup so that I can leave this setting on Left from now on.