I'm uploading an app manifest into App Studio that's an older version (happens to be 1.5), but when I try Install it using App Studio, it fails. When I go to the schema editor inside App Studio, it shows me it's changed it to Schema Version 1.9, which I think is the issue.
Incidentally, this user is having a similar-but-different issue: App Studio is generating a version 1.9 manifest which fails validation and stops side loading earlier today.