I need to go back and see if I can identify when it was working and when it stopped working, if you have any extra details about that let me know, otherwise I'll get back to you soon.
I did some checking and established it broke in Blocks version 1.6.7. (There have recently been breaking changes in the Gutenberg editor with WordPress updates which we have had to adapt to, and it looks like this was an unintended casualty of that.)
I've raised this with the developers and it is something they will give urgent attention to, so we should hopefully get a solution soon.
I'll keep you posted as soon as we have something.
Yes, it is. It is fixed in development, I'm just waiting for confirmation of when the fix will be released, and it should be any day now, there are a few plugin updates pending which just need to go through the normal release steps.