Stun mechanic errors in console

https://git.mythiccraft.io/mythiccraft/MythicMobs/-/wikis/skills/mechanics/stun

Stun mechanic works but errors out in console.

My setup in skills:

FishSmallNet:
  Cooldown: 5
  Conditions:
  TargetConditions:
  - mythicmobtype{t=SmallFishNetFishingSpot} true
  Skills:
  - message{m="&7You start fishing..."} @self
  - stun{d=84;f=true} @self
  - effect:sound{s=entity.fishing_bobber.splash;v=1;p=1;}
  - delay 84
  - skill{s=CatchShrimp}

Setup of the item triggering the skill:

SmallFishNet:
  Id: flower_banner_pattern
  Display: '&6Small fishing net'
  Lore:
  - '&8Useful for catching small fish.'
  Skills:
  - skill{s=FishSmallNet} @target ~onUse
  - skill{s=CancelDamage;sync=true} ~onUse
  Options:
   Unbreakable: true
   HideFlags: true
   AppendType: true

Log: https://pastebin.com/hAJH3PXM Paper 1.17.1 181 MythicMobs 5.0.0 7bb6c20a MythicCrucible Build 3586