I believe this already has been reported roughly 4 days before final release. And it is not solved. Since this was partially fixed quite easily, I would expect that this had been fixed, but it looks like this has gone under the radar.

I am also open to the fact that my CPU might be underperforming. But i see this unlikely.

Nether portal causing lag, this is under specific senarios.

I made a chunk loader using 2 nether portals, having droppers on each side to load each side of the portal. This works just fine when you're in the overworld no lag whatsoever (when you personally load the overworld part of the chunkloader. There is however a slight increase in time needed to calculate the tick reaches a peak of 30).

But if i venture far enough away to not load the portal in the overworld i get lag spikes each time an item from nether comes to the overworld.

I have the droppers on timers exactly at 9,6s so the other side never gets unloaded. I have a world that i built a little contraption which does this. Every 9,6s i get a lag spike where the time needed pr tick is increased to ~300ms it quickly drops back to 3-4ms. (when the chunkloader is out of you're natural player loaded chunks)

I have included a video of the lag spike and the world file. The chunk loader is at 1000 56 1065. There are command blocks to teleport you there. At -0 56 -0