Kodi file manager, write access to a usb storage router

I have a ssd usb attached to my tp-link AC2300 router. I have the user created with full rights, I can only see and copy the files from ssd to my tv box. I can’t delete, edit or copy via ftp on ssd from kodi file manager. Neither from CE nor from Android with the Kodi file manager. From Android I can do this with other file managers.
It would help me to be able to directly copy the backup files from sdcard to ssd, or other files that I want to use for a new CE installation, directly from CE somehow, without ssh or other not very convenient tricks.
I’ve found very little discussion about this and I still don’t know if it’s a Kodi problem, a problem with my router, or I’m not doing something right. Or maybe it’s not a problem, but for security reasons Kodi doesn’t allow this.
It would make my life a little easier if you helped me solve the problem.
Now I have to copy the backup files to a usb stick and then either put it on a pc and copy it to ftp, or restart the tv box in android and copy from the usb stick via ftp to ssd.


In settings, media, general, have you got ‘Allow file renaming and deletion’ turned on?

Yes, the settings are correct. On the usb storage attached directly to the tv box I can do anything.