Vaal Foundry impossible to kill rare enemy

Encountered a rare enemy that couldn't be killed in Vaal Foundry map, it didn't even have a health bar, i know it was rare though because it was marked as a rare that needed to be killed in the map, so i couldn't complete the map.
Also you can't get out of the boss arena unless you can blink or something.

I have had the same issue. The rare was in the floor, could only see it's top half. It could attack me, but I could not attack it.

Just had this happen to me as well the enemy rare was stuck under the Vaal foundry map. Did not have a health bar and could not be damaged but it could damage me. Could not complete the map.