I think it might have to do with the update to the terrain system they did; they mentioned that areas u already built (like ur old base) will be stuck on the old system and need to be manually updated with a dev command, and that the old system can be significantly slower now. I'll link the article so u can try the command near ur base and see if it helps!

I believe the command is called 'optterrain' but you need to have commands enabled for valheim, and most importantly make SURE you backup your world and character files first using gamesave manager or by backing the files up manually. Some people reported that it was damaging some of their buildings back then, so in case something goes wrong when you try to update to the new terrain system, you'll have a backup of your world to restore from.

Here's the article, I recommend giving it a small readthrough before you do it so you know what to do and what to be careful with.

https://screenrant.com/valheim-update-terrain-modification-system-iron-gate-patch/#:~:text=The%20new%20terrain%20system%20will,console%20command%20called%20'optterrain'.