I have this same issue on both the Switch and Xbox I have some footage of the slowdown, I can send the world file if you need me to. https://www.youtube.com/watch?v=JdaqgAcqy6s If you need more footage or clarification let me know. this is an issue in any world with enough stuff built.
I feel like fixing this should be a priority. Nevermind the unnecessary constraints on technical builds, which drive me crazy, but I can learn to (mostly) work around. But, I've been building a mob zoo on a family server with my 5 year old niece, and her zoo animals keep disappearing. This just seems completely unnecessary and it makes her sad, which makes everyone sad ...
it doesn't work now 😞
I have the same issue.