Screencast demonstrating the issue found
There appears to be an issue with the Reusable Gutenberg Blocks widget.
The issue is trigged when a reusable blocks widget is on the same page as wp show post and the content option is checked. When unchecked everything appears normal.
You can see this on a site I just relaunched using GPP https://mimifosterbooks.com/blog/ scroll to the footer and look at the first widget on the left.
I’ve covered all this in the screencast. If you find that this isn’t a WPSP issue please let me know so I can alert the other plugin author.
Love this plugin and version 1