What game modes does this happen in? (or what modes have you noticed it occur in)
What Troop/units are on your Team + The enemy team? What are their Traits?
Please confirm this is the correct steps to reproduce the problem:
Play a battle with Yao Guai
Select Yao Guai’s icon
Select the Weapon on the left card (when there are 3 cards available)
Notice the Gem Count menu popup
Click on the middle card, or the Traits card
Click on the Blade of Despair/Spell card
Notice that the Gem Count menu is not shown
Is that correct - or, are you closing the Troop and returning to the battle somewhere?