I was running into a lag issue on my server that I first noticed around 1.20.4, and I narrowed it down to a map area I had ( in dark oak hut ). This issue still occurs in 1.20.5.

The map area within these chunks cause major lag during world save or whenever the server autosaves (around every 5 minutes)

I have trimmed out irrelevant parts of my server's world for privacy reasons.

The lag is most noticeable while riding in a minecart and running the /save-all command.

Steps to reproduce:

1. Setup a vanilla minecraft server with this world file (attached and zipped)
2. Join server, build a little minecart track loop, and ride it while running the /save-all command.

You'll notice that the minecart will freeze in place for a couple seconds, and the server console will show a message "Can't keep up! Is the server overloaded? Running 2000ms or 40 ticks behind" or something similar.

This affects the server nonstop if the chunks are part of spawn chunks, and if not, only when these chunks are loaded.

Of course, breaking the item frames fixes the lag issue after a couple "/save-all"s.