Mutant Battle Arena hard crashes when a wither skeleton dies

Partner Rank: 1

Verification builds: 1.16.100.53
Regression builds: 1.16.20

Summary: Wither skeleton in Mutant Battle Arena hard crashes the game when it dies.

Impact: Hard crashing is extremely bad for maps, it rolls back game content and breaks game logic. In addition, this is a popular realms+ map. It makes them unable to be completed and causes negative reaction to players. Moreover we have no way of knowing why it crashes and so cannot fix it on our end.

Repro Steps:

1. Start a mutant battle arena game
2. Do /summon wither_skeleton
3. give yourself a netherite sword or something to kill it
4. kill the thing

Expected Results: The game should not crash

Observed Results: The game hard crashes without any asserts

Screenshots/Videos attached: No, it would be a video of it straight up crashing so would not be helpful.