Humm.
Was about to edit my post but @johnpoz was to fast.
Again, I took a user "001", etc etc see my image above.
So, I checked the manual (/usr/local/www/systemuser_manager.php and /etc/inc/auth.inc where the function local_user_set() lives) and put this function in debug mode (adding $debug=1; at the start of the function).
Logging should became more verbose.
Then, I did the thing one shouldn't do, I edited (deleted the line) the user "001001:*:2057:65534:002:/home/001:/sbin/nologin in /etc/passwd.
(and removed /home/001001/ also).
From there on : I had more vebose logs ***, no more problems. I could edit - and edit again - re-edit, delete, create, edit.
I removed the debug line.
Still, all ok, the error vanished.
[image: 1542381913338-3e69659d-5bb7-45aa-b2ee-2256c5fe2ba6-image-resized.png]
Curious.
I have this feeling that I touched the /etc/passwd file (system == FreeBSD maintained) and after that all was ok again.
I can't explain ....
** more verbose logs in the ....... captive portal log - not the system log ...
edit : I rebooted. Could edit a user just fine.
Strange - but solved