With the new Minecraft, some sound effects aren't playing at all times they should play.

Example: The item collection sound randomly doesn't play. I could't count yet, but I would say it's about every 50-70 items, that this sound is missing. Circumstances seem to be irrelevant: If I pick up many items in a noisy scene or a single item in a lonely cave with no other sounds available: Sometimes the sound isn't played.

Same goes for the sound when destroying blocks - the final noise of destroying the block is missing sometimes. Same goes for placing items.

When fighting creatures, the hitting sound sometimes gets lost.

I can't say if any other sound effects are affected ("passive" ones, not triggered by user interaction).