This is an odd one, I can't seem to repeat it but i spawned into a siege match as Grohk without his lightning staff.
There was no staff model in first person or third person but his hands were out like he was holding it.
Primary attack did not work at all.
Secondary attack would fire properly but has no animation just the lightning orb flying out.
I'm not sure if it's specific to Grohk, and it only happened once but it was pretty game breaking for me.
Has anyone else experienced this on Grohk or other champions?