I can't figure out what is happening...
Please watch the video.
Entity is increasing dramatically and they make my computer lagging.
When I restart the world, the entity count is reset and increase again.
Sorry, my English is bad but I think you can understand what I want to say when you watch my video.
Looks like the same issue I encountered with my spawners https://mojang.atlassian.net/browse/MC-10501
Very odd!