The Bug:
minecraft.used:minecraft.lava_bucket doesn't increase when filling a cauldron with a lava bucket.
Steps to Reproduce:
Create a scoreboard objective for tracking the use of a lava bucket and set it to display on the sidebar.
/scoreboard objectives add UseLavaBucket minecraft.used:minecraft.lava_bucket
/scoreboard objectives setdisplay sidebar UseLavaBucketFill a cauldron with some lava using a lava bucket.
→ ❌ Notice how the scoreboard doesn't increase.
Can confirm