I just updated my server from 1.15.2 to 20w06a an i noticed while some mobs spawn an stay spawned in, quite a lot of them appear to spawn an despawn instantly as shown in the brief video link. https://puu.sh/F84pl/b275218ae6.mp4
When visiting diff biomes and areas outside of the spawn radius, mob spawnage seems to proceed as normally intended
Is this still an issue in the most recent versions (currently that is 1.16.3, or the latest pre-release 1.16.4-pre1) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.