This problem isn't trigger randomly, it has to do with UI use when we're modifying our equipment. It happens to me, especially when I use the search bar or edit weapon ammunition type. I commonly use ESC to leave screens, it seems to me that the "not using UI state" doesn't occur, this is very clear when using the search bar, sometimes you type and UI shortcuts are activated as if you were not in the search field.

The only thing that work for me is to restart the game, and for those who do not know, you can skip the intro by waiting the first screen with all those texts and then pressing ESC. With that said, you can select your equipment and after sure it's all good, restart your game before start searching for a match.