When attempting to fill a canteen from a cauldron, it replaces the canteen with a waterbottle full of dirty water.

Thanks for the report!
This is a problem with Tough as Nails.
You can go report it to them over at https://github.com/Glitchfiend/ToughAsNails. Keep in mind that Tough As Nails is not currently actively developed, but I'm sure they will eventually get around to it.