Rapidfire cannon prevents akali from ulting

I had an unfortunate match where I put a rapidfire cannon on akali and she then did not ult the entire game despite having full mana. If it makes any difference in possibly recreating the bug, she was level one and already had Yuumi and Spear of Shojin equipped as well.

Perhaps it's because the enemies she was auto attacking were now outside of her ult range?

Anyway I hope this is not the intended behavior of this champion with that item, hopefully it's an easy bug to fix!