I had set up a pointed dripstone with a water source above a cauldron (no air block in between the dripstone and the cauldron) with 1 level of potion, in my survival world. At first it worked just fine, cauldrons with potions filled up just fine. But since yesterday it stopped working. However, the cauldrons do fill up with water or lava, depending on the source above.
I created a copy of the world and set it in creative to try and figure out what the issue is. First, i set the random tick speed to 1000 to speed up the process. Then I removed the signs I had placed on the dripstones. I also tried placing the dripstone with the water source to have a 2 block gap with the cauldron. Furthermore, I deleted some spare worlds I had to free up space in case it had something to do with that, and restarted my computer multiple times. None of these fixed the issue so far.
If I have missed anything I should've included, do let me know.
This was a bug that was fixed, see MCPE-131180.