The site is running under J4,2,2, Helix Ultimate 2,0,11 and SPPB 4,0,4. Because of this issue, I tried the latest release of SPPB on a local site where the issue is the same.
These screen shots illustrate what happens when trying to add a picture to image carousel. Clicking on « Folders » generate an error and a new preview page is visible (without undo, redo, preview and save) and no further action is possible. This issue also existed with SPPB4,0,3.
The screen shots are visible on the site : https://www.randouveze.fr/images/SPPB01.docx
Would appreciate your assistance.