Players have reported that two of the bosses in the new Sunken Temple Level-Up Raid, Dreamscythe and Weaver, are not spawning. This seems to occur when a group clears the raid up to this duo, leaves the instance and then return at a later time.
As groups returned on the second day of Phase 3 to continue their raids and found that these two bosses weren't spawning, some reported this straight to WoW Classic Senior Game Producer Josh Greenfield himself. Josh quickly responded and said that Blizzard is working on a fix to this spawning issue.
As players continue to work on clearing this new Level-Up Raid, it is looking to be the hardest one yet.