Working as Intended (But still should be fixed imo)
If it'll let you, try pressing f3+p ingame. This toggles the "pause on lost focus" option, which automatically pauses the game if you leave the window and go to a different program. I think the issue that you're having is that the game thinks that you're currently interacting with a different program. if you're using windows, and you can't use f3+p because of the pausing, you can manually edit the option by going to %appdata%\.minecraft\options.txt and setting the option "pauseOnLostFocus" to true
durability most likely wears down. give yourself an unbreakable elytra with
/give @s elytra 1 0 {Unbreakable:1b}
this is because signs are treated as a block, but paintings and item frames and paintings are actually treated as entities.
how many other hostile mobs are in the world?
have you tried converting to 1.12.2 and then converting that copy to 1.13?
Ah yes, this is referred to as ghost blocks. They are really very annoying but are fixed in the 1.13 snapshots
Shipwrecks can also generate inside the ocean floor, and into the sides of underwater hills
I think that it is leaves as well. Changing graphics to fast fixes the issue, and disabling fire tick does not.
I believe that the cause for the lag is leaf rendering - the client tries to render things behind the leaves because they're slightly transparent, and renders leaves behind that in layers of increasing lag. When I switch to fast graphics, the lag vanishes. Also, disabling fire tick does not stop the lag, so it is not a spreading forest fire that causes the lag.
Are the villagers near doors? they won't breed if there are more villagers than doors.
carpets have the properties of the block under them, so if that block is spawnable, then so is the carpet. What ilmango does is make the carpets two layers thick. do that and it should be spawnproof. also, this farm is optimised for Java Edition. try looking for a Bedrock Edition farm.
My friend on X-Box one is having this trouble, too. Nothing is working!
Please post screenshots