Couldn't delet Photo's

[Vo]

Hi there,

how is it possible to use the <DEL> Key right? As if i mark a Picture,
and hit the key, Digikam tells me:
'Couldn't move picture nameofpicture.jpg to collection trash'

and why i start Digikam 5.4.0 (under Ubuntu 17.xx) from console i saw
something happend, but couldn't imagine what this is all about.
Look here: https://pastebin.com/HwLRD72X

I searched google for this problem, (re-)setting the Userrights for the
folder .dtrash, and some other things....

.. but no solution at the moment....

Thanks for reading
Vo.