After doing some tests on a couple of different server environments, I can conclude that the issue seems to be a conflict with the WordPress preview screen and the Access plugin, for website's hosted at WordPress.com.
( this is not specific to form edit link as you'll see the same error if you try to preview the drafted page "Research" )
I've shared these findings with the concerned team for further review and will keep you updated with the progress.
I'm happy to update you that this will be fixed in the upcoming 2.8.10 release of Toolset Access.
Meanwhile, you can also use the updated "post_preview.php" file from the following link to replace the one on your website in the folder: /types-access/application/controllers/filters hidden link