Burning items sound effect seems to be inconsistent

When throwing items into lava, the sound effect seems to be very inconsistent.

Footage: https://www.youtube.com/watch?v=VE2_5F_oT_U

 

Note: This was on a 1.15 Pre-release 5 server, upgraded from 1.14.4. I don't think the fact that it's a server is important to this bug, but I haven't tested in single-player.