Gustavo Dominguez

I encountered this bug after using a ticking ender pearl pack, somehow when used they were creating ghost ticking areas that couldn't be deleted from in game.
strangely, you CAN see these ticking areas if a normal ticking area is created, with the command /tickingarea list. if there are no ticking areas, /tickingarea list returns nothing.
this could be a big issue for players that have ticking ender pearls and are using stasis chambers for returning to far away places, as they will create ghost ticking areas, I personally had about 10 ghost areas from a communal stasis chamber.

attached a ticking armor stand and a ticking pearls pack for testing 

this bug is considerably worse than we thought, or at least it has gotten really bad in .210 for some reason.
my server specs: Ryzen 2700@4ghz, 16 gigs of ram@3000cl18, running Trapdoor for profiling, Windows BDS for .210, locally, max threads 0 (or as many as it can use).
for this test I used Trapdoor for profiling. the profiling function profiles 100 ticks and gives you a breakdown of what part of the game uses more MSPT(miliseconds per tick). the limit is 50 MSPT, where the game drops below 20 TPS.

I created a new world in simulation 6, render 24. Placed a double chest with a hopper, and took these metrics with them empty:

5 mspt, which is pretty much just the player ticking the chunks around him.

after this, I filled the chest and hopper with shulker boxes filled with iron ingots (I discovered this issue in our iron farm)
This was the result:

36 MSPT only from ticking the chest and the hopper! I profiled multiple times, it kept giving me 40 mspt.

after breaking the hopper, I got this result:

as you can see, metrics went back to normal.

Shulker loaders are a very common storage solution in survival worlds, and a single full hopper pushing is enough to lag my very much overkill server! this could create enormous amounts of lag for slower servers!

Still happens in .210 and .220, this bug has actually made one of my server farms incredibly hard to make, because we want to deliver the xp somewhere, but we can't see it.

Can confirm this happens in singleplayer and with BDS

using a /setblock portal before it dissappears will also sometimes freeze the game, crash it or stop rendering blocks on the other side.

edit: wasn't able to replicate it, but you get similar effects when going into a nether portal tile from the end to the overworld.

Windows 10 here, still happening in 1.12.0.11,  leaving a vote here hoping it gets resolved.