MB Blocks: Not Saving Order of Grouped Fields

I can change the order within the group in Gutenberg (in my case menu_items), but when clicking Update it does not get saved. E.g. when I reload the page in the backend, it still shows the old order. Everything else however saves correctly.
I think this issue started recently (maybe around the WP 5.3 release).
I am using all the newest plugin versions.

Thank you for checking into it!

https://pastebin.com/wivHUPeD