Rune Chain Spell not working - after selecting friendly troop

[Harakiri]

The spell will increase its damage if you sacrifice runes from one of your troops - once your troop is selected - however, you cant cast the spell anymore - moreover - if you reselect the spell in the spell book - it will now say it does the 250% damage on the enemy target - but it wont, it will still do the normal damage without enhancement.

Sometimes also, after selecting a friendly troop - the game displays the hourglass for a unspecified amount of time