The bug

The summoner of a vex is not reset once it is dead.

How to reproduce

1. Spawn an evoker
2. Summon a villager next to it

   /summon villager ~ ~ ~ {NoAI:1b}
   

3. Wait for the evoker to summon vexes
   → The vexes attack the villager
4. Kill the evoker

   /kill @e[type=minecraft:evoker]
   

5. Prevent the vexes from starving

   /execute as @e[type=vex] run data merge entity @e[type=vex,limit=1] {LifeTicks:2147483647}
   

6. Switch to Survival or Adventure mode
   → The vexes attack you
7. Switch to Creative or Spectator mode
   → The vexes attack the villager again even though their summoner is dead and they normally don't attack villagers