Invulnerable Unearthed Urchin Mobs

I just did a detonator mission and the monters that came out in masses called unearthed urchins cannot be harmed by lightning or fire damadge.

Found this post through Google.

This is still happening. Died twice today to those. First time I thought my projectiles were flying over them and not hitting their model/collision and got overwhelmed. Second time it looked pretty obvious they werent getting damaged at all.

Using Chaos Damage. 100% sure no Chaos Immunity node/chest was blown up in both cases as well.

This just happened to me. No lightning immunity or other modifiers on them, using Archmage Spark Stormweaver.