Platform: Windows

Date & Time:
12/23/2017 1:00~2:00 PM EST

Frequency: Did 3 runs, happened first 2 runs not the 3rd.

Character Name: Nekonohimitsu

Race: TarutaruF

World: Quetzalcoatl

Main Job: SMN99

Support Job: RDM49

Area and Coordinates: Yorcia Weald [U] (Marjami Delve), Plaguevein spawn area

Party or Solo: Party, 3 players with 3 trusts and 4 players with 2 trusts.

NPC Name: None

Monster Name: Plaguevein Bats

Every time we kill the Plaguevein Bats, a hidden bat stays alive that we cannot target but has enmity on us. This prevents us from spawning trusts.

Party consisted of SMN/RDM, THF/DNC, BST/DNC the first time. The second time a BLU/WAR joined. Trusts were Ark Angel EV and Shantotto II the second time. Koru-Moru was used as well the first time.
It's possible that the bats were stunned with Shock Squall when the boss died, but my log does not go far enough back to get specific information on what happened when the bats died. The first time hate was on the THF after death, the second time it was on Ark Angel EV. Hate changed depending on actions, and was removed when players logged out and trusts were despawned. When all players lost enmity they went idle and began walking back to their spawn location.