Whilst Playing the invasion modpack by Darkosto I was trying to fight the wither. Due to the "harcore wither" mod it grants the wither the abilty to teleport. This however is not affected by the enderjammer.

The mod creator for Hardcore Wither doesn't trigger the EnderTeleportEvent when the wither teleports - its their call whether or not to do so, but if they don't I can't block it with the jammer.

thanks