Invisible monsters in expedition (from strongbox)

Bug Report ID: #3637125522

In the map I was running I blew open a strongbox, which spawned monsters but they are invisible. I can mouse-over them to see what they are and know where they are (sometimes health bars are also visible) but I cannot see them, nor do they take any damage from my (AOE) attacks. These invisible guys were still able to hurt me and killed me several times as I tried to clear the rest of the map.

Edit:
Further information: I tried multiple things to "solve" this issue. I tried leaving the map and coming back and I tried switching from Vulkan to DX12 (which caused me to get thrown back to main menu so I had to re-enter the game as well).

Same issue, same cause - strongboxes during expedition.

Bug reference number is 2506015529