I recently update JCE to version 2.9.55. I have found that NON Super Users are able to use a modal pop up dialog box in Akeeba Tickets. In opening the ticket with Akeeba I received this response:
"This looks like a JCE bug which was fixed in the latest release a few days ago.
Your problem here happens in the editor, before our code runs. Our plugin says "when the user clicks this button you must display a modal dialog with such and such URL opened in an IFRAME inside it". JCE shows the modal background blocker overlay, but does not open the modal. This was, indeed, a bug that JCE had and fixed very recently, in version 2.9.52, see https://www.joomlacontenteditor.net/support/changelog/editor.
If updating JCE does not help please contact its author, Ryan Demmer. He's more than happy to identify and fix this kind of issues."
Here is a link to a screen recording showing the issue:
https://watch.screencastify.com/v/Pui2DPqGyBsRt7RXxp25
Any assistance you can provide would be greatly appreciated.
Eric