As my sites have gotten bigger, I've noticed that I can't always save one as another is publishing.

Sometimes I even got the spinning beachball and the computer hangs.

I thought this was a problem with RapidWeaver. But it turns out that it's a combination of RW and Dropbox. I keep the site files on Dropbox and McFiach (my MacBook Air). The macOS daily maintenance routines sometimes make things worse, I'm insomniac and tend to keep weird hours.

The best solution I've found is to work on only one site at a time. When that is uploading, I do something else.

If I do work on a second site, it's vital not to save that second site until the uploads finish.