After doing quite a fire bit of testing, I can say that my cauldron routing issue is caused by teleport system update on the mist and bat teleport.
Firstly, I've found out that teleporthere-vampire_mist and teleporthere-vampire_bat were scrapped and replaced with vampires_spiritpowers_flyasbat and vampires_spiritpowers_teleportasmist. This update was not mentioned in the patch notes. (Basically the teleporthere-vampire_mist and teleporthere-vampire_bat uses the GoHereSuperInteraction to teleport, however the update now uses TeleportStyleSuperInjection instead)
Secondly, from my experience modding, I've remembered that the Spell Teleport have testset distance of 7 which disallow the caster to teleport. However I do believe that the mist and bat teleport do not have any form of testset distance which could be the issue as they kept on teleporting on very short distances, which with the old system would have them walk.
So I decided to write a small mod to test this, and using the system did show that the updated mist and bat teleport system was the issue.
The current workaround is: Vampires with Bat or Mist Teleport Enabled OR Spellcasters with Mist or Bat Teleport Enabled (Applies to Vampiric Teleport Spells) MUST disable their teleportation before using the cauldron otherwise they will LEs will generate and the Sim will cancel the interaction.