Update from Miro support [RESOLVED]:
Great news - the team released a fix for the issue with scaling objects and frames. I just tested it on the board you shared with us, and I could no longer replicate the issue.
Could you please try again and see how it goes on your side? You might need to log out of Miro and log back in to ensure you're working on the latest version.
I have tested on a few boards where I was unable to resize frames (and all objects inside) and it is working as expected.
I will mark this post as resolved, but if you have cleared your cache and signed out and back into your account, and are still experiencing the issue, please reply to this post.