Sometimes NPCs are no longe visible, we had this happening with Cats, Polar Bears and Cows (but not with Player-NPCs or Villager-NPCs)
The NPC is no longer visible, but if I teleport to it (/npc tp), I go to the position where the NPC should be. If I teleport the NPC to me (/npc tphere), it is visible again.
Citizens: Build 1456
Server: git-Paper-963 (1.11)
Getting this error as well, happening with my skeleton and zombie NPCs.
The NPCs seem to be dying randomly but they don't respawn even though I've set their respawn delay to 1.
Forgot to mention that I'm running spigot 1.10 and all the NPCs seem to respawn if I do /citizens reload
Can confirm that this bug exists on build 1420 on the latest Spigot 1.10.2 build. Currently cannot confirm on the latest build on either 1.10.2 or 1.11.