Steps to reproduce

1. Create a flat world with simulation distance set to 4, and daylight cycle off (so monsters don't interfere).
2. Place a bed and stay near it.
3. Spawn a villager.
4. Set up repeating command blocks to kill all raid mobs.
5. /effect @s bad_omen
6. After each raid ends, repeat step 5.

Expected result

Each raid gets kill by the repeating command blocks. You can continue steps 5 and 6 indenfintely.

Actual result

Eventually, you'll have a raid that cannot be targeted by the repeating command blocks because it spawned outside of loaded chunks. That raid eventually times out.

Sometime, there will be a chance of wave spawns outside 4 chunk simulation distance or more than 64 blocks away in an unloaded area.