I was playing around with custom spawners but when I used the tag "MaxNearbyEntities" , the spawner froze and nothing happened...
What I expected to happen was...
... the spawner would just work as normal. It would not freeze and it would stop spawning mobs if there was already a certain amount of mobs around the spawner. (Just what the tag does, or should do)
What actually happened was...
...the spawner froze and did absolutely nothing.
How to reproduce:
1.Give yourself a command block and place it down.
2. Use the setblock command to setblock a custom mob spawner with the "MaxNearbyEntities" -tag.
/setblock <x> <y> <z> minecraft:mob_spawner 0 replace {EntityId:Zombie,MaxNearbyEntities:2}
3. Power the command block and notice that the little "mob" the spawner inside freezes, there are no particles and that is does nothing.
Attachments
Comments

Oh yeah, that's a shame... Accidententally made it day...
However, when I tried to make that spawner while it was night, it still didn't spawn any mobs. And this bug seems to occur randomly, I managed to get it to work a few times.
EDIT: If you add 'RequiredPlayerRange' the bug doesn't seem to occur.

Ah I missed that! This works as intended. You need that RequiredPlayerRange or there will be no tag to indicate when the spawner should actually spawn.
Here's a template
setblock ~ ~1 ~ mob_spawner 0 replace {EntityId:PigZombie,SpawnData:{Pos:[-463.5,5.0,960.5],Equipment:[{id:red_flower}],Anger:32000},SpawnCount:1,SpawnRange:50,RequiredPlayerRange:3,Delay:1,MinSpawnDelay:50,MaxSpawnDelay:50,MaxNearbyEntities:4}
Oh okay, thank you! Then this topic isn't necessary anymore... I'll remove it when I've figured out how 🙂
And I've got a question, how do you make a template like that or make the text bold or italic? <b></b> doesn't work...

Mods can marks this as works as intended.
For formatting on Jira, go here
https://jira.atlassian.com/secure/WikiRendererHelpAction.jspa?section=all
The template is used was pasted inside {code } tags
I've had this bug many times. I'm just not sure there is a specific way to reproduce it properly. Seems to bug out randomly.
However, in your screenshot, that spawner will not spawn any mobs since it's in full daylight.