Erm guys re-read the OP

Originally posted by ﮱﮔutex:

A day ago I was able to play Valheim on my main base, with no lag stuttering or low FPS. Yet, after I went to Mistlands and then returned to my main bases via the Teleport. I was getting 4 FPS with nearly zero GPU usage and about 4% CPU usage

Unless his base built itself up while he was away, there is no way its a normal performance/optimization issue.

Either a bug on the save, or patch messed something up with drivers.
4fps is real low... it reminds me of gpu running in power saving mode.

Also having 30fps in mistlands on 4070ti ??? thats an issue already. So possibly extension of existing problems. I would start with GPU driver reinstall. and check / disable stuff running in the background, could be some runaway app