Jarl's call of battle ability bug

[TigersClaw]

Hello.
I have looked for it but it seems no one has encountered this bug yet.

After defeating the huge dead spider in the cave, I'm moving to meet Rorun.

I defeated the 1st group and had no issue with using call of battle. Then, I meet the vampires and it says there is "no target for this ability". But I do have level 1-4 units that have already used their turn.

Anybody seen that before? Have you found a fix? Thank you.

UPDATE: I have been able to reproduce the bug. If I go and fight the necromancers right after the spider, I do not encounter this bug. However, if I leave the cave to return to Vestlig to replenish my troops and come back, then I encounter this bug. Hope this helps.