Short version: Dripstone with lava source above may replace water filled cauldrons with lava filled cauldrons.

Between 1.18 snapshot 7 and RC3 me and friends been playing on a multiplayer server. I have spotted an interesting behavior:

A friend built a "lava farm" using cauldrons, dripstone and lava.

One day i took out the lava with a bucket. Because we planned to move the farm, i removed the lava source and the dripstone. It started raining, and the cauldron filled up. (i am not sure if partially or completely, but you may figure that out using gametests)

We then actually placed back the dripstone and lava source because our new location has not been ready yet.

The water filled cauldron got replaced by a full cauldron of lava.

I could not reproduce it in a local world yet, nor have i managed to join back onto the server due to constant disconnects if playing without a VPN, so i can not provide any video or pictures sadly