sounds like you've imported some issues as well.
try erase and fresh install of the latest compatible macOS - which'd be ventura or sonoma.
then set it up how you like it.
if it's still iffy then you indeed have a problem.
if everything seems normal proceed to the following …
manually add in your home folder contents from the backup.
example - file/import in photos.app, music.app and so forth.
manually drag across your documents, movies, etc, to their respective folders
should run sweetly after that.
i't's a tad time consuming but you should end up with a clean fast machine. 🤞