I have created a "form admin" role with three permissions only: "Access the webform overview page", "Create webforms", "Edit own webform" (Drupal 9.3.7, Webform 6.1.3). The user can create a webform but when trying to add an element then the page goes into "reload loop" (see two screenshots). The issue disappears only if I add "Administer webforms" permission or enable "access webform configuration" for that role on that webform (Home > Administration > Structure > Webforms). Both those additional permissions come with warning and I don't really want them to be enabled (they somehow contradict concept of "Edit own webform").
Further investigations showed (again with only "Edit own webform" permission given) that I can use [source] to create form content but if I try to edit it in [Elements] tab the edit panel appears and instantly disappears leaving "xxx has been updated".
Console throws: "TypeError: null is not an object (evaluating 'a.contentWindow.document')" and "Error: cannot call methods on dialog prior to initialization; attempted to call method 'option'". But again, with "Administer webforms" permission on, this issue does not exist and everything works as expected.
I've found this old question https://www.drupal.org/project/webform/issues/3021948 and I relate to that but the answer given there doesn't seem to be working for me.
I ask for help, comments, suggestions?
best regards
Nikodem