I've had the same thing happen.
Hero: Donya
Specialty: Defender
Hero Ability 'Command' when used for the second time in a battle will lock all other units and only allow the caster to move/fight.
This lasts until the 'Command' ability comes off cool down. Casting it once more will again lock all other units save for the caster to move/fight.
Caster of 'Command' can still use other abilities before and after the second casting of 'Command' (the second casting is when the bug shows.)
Units that can 'Counter Attack' will do so when attacked, but only once.
'Command' does not need to be cast on the same unit twice, just cast twice in the same battle.
Hitting the Auto-Play button at the top right will have the casting unit move about randomly, the unit will cast 'Command' each time it's up. I did not witness the unit attack anything, just walk about and re-cast 'Command' when it was off cool down.
Hitting the Auto Resolve button at the top right = Auto win. No other casualties/damage is taken, even from units that can 'Counter Attack'.
If the 'Command' ability is not used a third time, the armies unlock and you can continue the battle as normal. Casting 'Command' at any time will lock the armies again.