As seen in the attached images, I've had no issues with Papulatus Clock but when Papulatus came out I couldn't attack it/receive any damage from it. The hp bar at the top of the map is also missing.
I have the same problem. Only happens during the daily 2nd run. When my SE mule got closer to my NL and papa, SE mule couldn't see papa in the window, only showed in NL's
Found a quick fix. After the 1st run has finished, <forget the quest, go to take the quest "protect ludibrium" again, then the 2nd-stage-papu is fine to attack.
I've tried many ways to make it not happend And figure out u need to kill all the high dark star before latus comes out. Try it!!!
This seems to happen with monsters that are spawned from another mob. IE: dark wyverns from Leviathan, Pap's 2nd form, etc.