acl - create item - suddenly "Warning: You are not authorized to execute this task"

Meanwhile, a second client reports "sudden" lack of permissions to create and/or edit content items.

J 3.9.1
FC 3.2.1.15
My user in question is "manager".

User's "Advanced Permission Report" is unclear to me. I attacheed a shortened version of that to my reply.

Hello

if some extension changes the ACL permission of "Joomla article manager"
then flexicontent will copy this as its own permissions

it must be some 3rd party extension that is modifying modifying the permissions

Permissions of "Joomla article manager" in both cases look good. Please see attached screenshot.

Hello

Questions

1. Is the message shown after clicking item form save ? , then it could be due to a 3rd party plugin doing ACL checks

2. If you edit the category of the item , then w check

3. do you have a test that i can do tests, or can you provide copy of the website ?

1) No, the message "Warning You are not authorized to execute this task."
is shown on page-load (not on save) of the events:
- list items (of any type, also listing of all items)

The message is not shown is not shown on these events (e.g.):
- create content item (e.g. /administrator/index.php?option=com_flexicontent&controller=items&task=items.add&typeid=2&maincat=. Content Item is saved.

2) >> edit the category of the item , then w check
Do you mean by that: ~"open, cat, save cat, check agein"?

3) Yes, I'd be happy to provide you with BE-access for both live websites via PM.
But maybe it's enough -with above info- for you to put me in a position where i fix the problem?

Thanks!

ok, I think, I fixed it, doing two things:
1) unbelievable but true: clear all backend-caches.
fixed all but one follow-up-error: "Call to a member function isSite() on null" on "list categories" with Setup Joomla 3.9.1 / php 7.2 / FC ~Dev-Preview 3.?? (had gotten a direct link from you in a previous thread).
2) fixed that follow-up-error by downgrading from above now unknown FC-version back to FC 3.2.1.15