Yasuo Q Tornado Bugs upon ulting an enemy/Steel Tempest stacks resetting.

If you ult an enemy with full stacks of Steel Tempest still prepared (courtesy of a Zac or the like), Yasuo loses his stacks of Steel Tempest but he keeps the indicator as if he could use his tornado, which he can not.

In other words: Can't use tornado after Yasuo's ult finishes; Tornado's indicator remains extended period of time despite not being able to cast it. Yasuo can still Q, however. And, no, this is not a case of the tornado expiring.

I've encountered this bug twice today in ranked play with an allied Zac both times.