FYI WP Show Posts and Nextgen Gallery It has taken me hours to track down this conflict.
When using the block editor if you insert a WP Show Posts shortcode into a shortcode block and try to save the Page/Post it will generate a JSON error and not allow the save.
It generates the error message: Updating Failed: Unexpected token > in JSON at position 0
Agreed, nothing on the WPSP side causing the issue. That’s why I posted it as an FYI. I spent 6 hrs. over a couple of days tracking down why I suddenly couldn’t save a new home page. When I found the conflict, I decided to post in case someone else starts looking for why they suddenly get that error message.