NPCs appear slow after flight reach destination

[wangsiw1]

My azerothcore server is running on the WSL2, only for myself to play solo on the same machine. Since a time year or two ago, I noticed that it takes extra seconds for NPCs to appear and my character to be dismounted when reach the destination after taking flights across the world.

Something I tried but none of them worked:

• Enable "PreloadAllNonInstancedMapGrids", thought it will preload all NPC and won't unload.
• Increase "ThreadPool" and "MapUpdate.Threads", thought it needs extra power
• Move server binary and data folder from "/mnt/c/..." to native WSL storage "/home/username/...", Gemini suggested this. I know there is performance loss accessing Windows storage, although not a obvious difference in my setup.
• Some other small changes

I wonder if it's just me having this issue or it's common that nothing is special, and if anyone can suggest other things to try