Summary
Sometimes the mob's health becomes NaN and players cannot kill it. sudoskill of damage is used when this occurs.
Steps to reproduce
Mobs file https://pastebin.com/KGa0tbqy
Skills file https://pastebin.com/xjrbXcVi
The mob was designed in the way so that players can only deal damage to it when they are not holding items with the specific name. However, if the player is hitting the mob with an axe or without anything, the mob's health becomes NaN and doesn't die.
Current behavior
A video of the bug happening. [Legacy attachment omitted]
It is found out that the problem only happens if the player is not holding anything or is holding an axe. The problem won't occur and the mob dies normally when the player is holding other items, swords, trident or shoot it with arrows. Setting ignoreimmunity=true or false does not affect the issue.
Intended correct behavior
The mob's health should not be NaN and should die even the player is not holding anything or is holding an axe.
Debug log snippet