Thank you for the quick response. Unfortunately, I checked my server error log, apache log, and error_log.php. None of them had any additional error messages for this.
I had also tried this with an earlier version of VC 5.1.1, which is why I decided to upgrade to see if that solved the problem, which it did not.
I read the changelog of VC 5.1.1 and this was at the top of the file:
04.04.2017 – ver 5.1.1
Added: extra security check for grid ajax calls to harden security
09.03.2017 – ver 5.1
Added: Element Id for all elements
Added: Image size control for Grid Builder media elements
Update: Grid Builder Backend editor style user interface
I sent you an email with a link to VC 5.1.1, so you can test this version.
Thank you again!