I've been playing using a custom ruler using random map.
I hypnotized 2 warg riders and have both in the same army. Whenever the 1st rider using charge the second rider moves insteadof the first freezing the battle. auto play doesn't help only instant battle resolution will finish it. repeated this several times n it happens every time.
Another bug with them that happens ever so often is using their skill that ignore defense will sometimes freeze the battle as well and the -defense shows above the other warg rider instead of the first.
One note i haven't tried charge using the warg rider which moves second instead of the first for charge or using defensive move.
Oh and the custom ruler i was using was the wilderness one.