Migration gone wrong

So I did a migration for a client. It’s a new site that I hosted on my server until it was finished. Now I’m migrating it to the client’s server where he has his old site overwriting the old one. I’m using the All-in-one WP Migration plugin.

I’ve done this before with no issues. But this time, not sure what happened. The site is getting an F in GTmetrix, because “Serve resources from a consistent URL”. If you look at the details, there are two URLS for multiple CSS and JS files. For example:

mysite.com/wp-content/cache/minify/35627.css
mysite.com/wp-content/cache/minify/35627.x93104.css

Also, when I first migrated the site, it was around 400mb. Now when I back it up it’s around 1gb. What could have gone wrong?

The page I need help with: [log in to see the link]