When a player dies in Cloudrest, there's an uncommon chance that their shade, or "shadow" as Z'maja calls them, will bug out and be invisible. Whether the shades drop into the ground, like the dwemer spiders in Halls of Fabrication after activating Roar of Alkosh just before the Archcustodian, or the shades just aren't appearing, the dead player cannot be resurrected. To manually fix this bug, the player has to re-log, and if a support role such as tank or healer receive a bugged shade, it is almost entirely a wipe. I've had people tell me this particular bug has been around since Summerset launch.
I've tried looking for a similar bug report post on this matter, but I honestly couldn't find one in the short 5 minutes that I tried. It's pretty well known within the PvE community, but I'm not sure if it's been addressed anywhere. Hopefully this will spread to the ears of the devs and ignite a fix. Thank you for reading.