[Gameplay] Unable to use abilities as Pantheon

When playing as Pantheon, casting your W spell "Aegis of Zeonia" on a target that then becomes untargetable such as during Fiora ult and possibly stealth mechanics like Vayne Tumble, Pantheon will be unable to cast any spells besides his W, including even "Recall." The only fix to this problem is casting Pantheon's W onto a different target which will then allow you to cast other spells afterwards. The other abilities are not grayed out and appear to be fine but will not work. I had a screenshot while bugged however, it isn't possible to tell that you are bugged from screenshot alone. This occurred twice to me in one game that had both Fiora and Vayne so I cannot be 100% sure which champion caused the issue, or whether both did.

Steps to Recreate:

1. Pick Pantheon.
2. Have Fiora or Vayne on enemy team.
3. Cast Pantheon W onto enemy champion right as enemy Fiora "R"s or Vayne "Q"s.

Result: Be unable to cast any spells until you cast W onto another target.