In panopoly_magic, for the live preview of blocks, we are currently capturing all validation errors, clearing them, and then displaying them in a custom way.
This is necessary for automatic live preview, because otherwise, the form will jump around (as validation messages are added) and some form elements may lose keyboard focus.
However, this is totally unnecessary when using manual preview, because the user clicked the "Preview" button and so we don't need to worry about the form changing or focus being lost. In fact, it is a much better experience to see the form validation errors right on the form itself, instead of messages within the preview box.
So, let's disable the capturing of validation errors when using manual previews
Active
3.0
Magic
This new patch will clear error alerts in the form when the preview is updated. Otherwise, validation errors on the form won't be removed once they are corrected and the user clicks "Preview".
Tested this on a child distribution and it's working as expected.