There is a he performance problem with the 2x2 buildings especially when using the chisel profile but also in the default one.

This seems to be related to how the 2x2 buildings are generated and saved in the chunk data.
This causes the following bug/lag issue:

1. Placing any kind of block especially light surces like torches causes massive lag for a short duration.

2. Breaking any block in these buildings or above and below them (same chunk) results in the same super lag spike for a second or two.

From what I could get this only happens in the 2x2 buildings so basically the ones with the checkerboard flooring. (In the chisel profile that I mainly use it’s the gray concrete and quarts blocks).

My main guess is that it’s related to how the chunk data gets saved for the blocks when generating the 2x2 buildings. So that every time a block update happens in this chunk there is a huge performance spike when it has to check the blocks in the chunk data!

It doesn’t happen in any other building. Only the 2x2 buildings (especially datacenters and libraries)
Also: The faster the pickaxe (mining speed) the more noticeable it is!

Maybe it’s a Mod conflict than. I had it happen during testing in a world with just the lost cities but it can happen way more frequently in my modpack, maybe you can give it a try if you have the time and pinpoint it. It only happens in the lost cities 2x2 chunk buildings. (Turned the spawn rate of them down which is sad as they were quiet a nice find) EDIT: Packname Dimension Zero Lost citys is set to be used witouth world selection.

Hmm. There is nothing special about those chunks and I have never encountered this myself. Very strange

Does it happen if you do so on top of these buildings.