well as you can see in my title i am a developer (i dont do html much tho)
i would Disable that MOD and try again, Anything that Affects the Game that is not Default is considered an Addon or Mod
i have no idea what ‘html or javascript’ your running but i would suggest unless tons more people start having the same issue thats likely the cause (assuming you dont have Other addons or mods you neglected to disable)