Also experiencing this issue... glad to see it's not just me.
To add to it, I've just been able to save to Dropbox with no issue, but I seem to be unable to save a local file at all. Whenever I choose to save local I get an error
"Unable to save project. Try checking you have permission to save in the chosen location. Alternatively try saving a different way."
I thought I was about to lose a bunch of work until I thought to try Dropbox