Hi @krievinshj,
Thank you for bringing this to our attention!
This should now be fixed with 1.4.0.1.
Kindly let me know if this is the case on your end.
It appears that you are selecting the Heading block in the screenshot you provided, so the generated preview is appearing as expected.
To clarify, it solely generates the block itself, and not anything surrounding it.
Please let me know and we’ll go from there.