Minecraft version
Minecraft 1.17.0, using Fabric 0.11.3

Mod version and malilib version
litematica-fabric-1.17.0-0.0.0-dev.20210616.033538
malilib-fabric-1.17.0-0.10.0-dev.22+beta.1
other mods:
g4mespeed-1.1.4-mc1.17-pre2-release
lithium-fabric-mc1.17-0.7.0
minihud-fabric-1.17.0-0.19.0-dev.20210608.211830
modmenu-2.0.0-beta.7
tweakeroo-fabric-1.17.0-0.10.0-dev.20210608.211857

Description of the bug
Schematics created in previous Minecraft versions, when pasted in a 1.17 world have all cauldrons inside of them empty, even if originally they were filled. The schematic also displays that the cauldron should be empty, even though the same schematic said it should be filled, when in a previous version of the game.

Expected behavior
The schematic should show and also paste in correctly the cauldron's fill level.

Steps to reproduce the behavior:

1. Create a schematic in a version prior to 1.17 with a filled cauldron
2. Enter 1.17.0
3. Load in the schematic
4. The schematic should show as the cauldron not being filled, even when it should.

I think they changed the block state properties in 1.17 due to lava cauldrons now being a thing as well. This will need a schematic converter/updater to update/fix the block state.

I started on such a system about a year ago, and it's like halfway done or something. That system will still need a lot of work before it's complete, and also since it's being developed in 1.12.2, it becoming available in the recent versions also needs all the other stuff from 1.12.2 to be ready to be ported. So no idea yet when that conversion/update system will arrive in 1.17.

Well obviously a simple "hack fix" could also be added just for the cauldron, but it's not a proper general long term solution. And since there are also other blocks that have changed over the versions, a proper system for doing cross-MC-version conversions is needed anyway, especially if people want to convert anything between 1.12.2 <=> 1.13+.