Hi there! It is a bit hard for me to know exactly what is going on here. If you can end the turn and move a new puppet etc. then I doubt it is something wrong with the Action, as that would likely stop the action queue and prevent any further actions from occuring (or at least throw an error).
Since I don’t know what you have modified I can’t give you the exact answer, but these are the steps I would personally use to investigate this: In BP_Ability add a breakpoint to ServerInteract. This is the event that should fire when you click a valid tile with any ability. When you click the enemy to attack it, it should trigger the breakpoint. From there keep clicking Skip and see at which points it breaks off before leading to the attack. Consider comparing this by doing the same in a fresh project and see where they differ. Perhaps this will let you solve the problem on your own. If not, report back to me on the behavior and I’ll weigh in.