Spells Not Loading (gameplay)

Loading into a game and I believe that if you alt-tab before loading screen starts or maybe a tad later, when you're finished loading into the game, none of your spells will cast unless you actually click the spell and cast it with your mouse.

1. Get into game.
2. Just as loading screen starts or maybe earlier alt-tab (may have something to do with windowed borderless mode).
3. Finish loading.
4. Test a spell to see if it casts.
5. If it doesn't cast, quit game and reload and spells will cast as normal.

I've gotten this bug probably 1 in every 30 games i've played.