Unable to save changes in text file

After I open a text file in jota text editor or totalcmd editor, I get a file protection error when I try to save changes.

The error message disappears so fast that I can’t catch all the wording, but basically it can’t overwrite the file.
I found that if I open from the owncloud app I can use the totalcmd editor. But with the jota editor I must use save as and navigate to the owncloud folder select the original name and overwrite, but I can’t use save directly. The error message says that the file is downloaded from a content provider and can’t be modified. When I try to edit from the Android downloads view, the jota is the same, but the totalcmd also must use save as, select the original file, and then I can overwrite.
I should be able to overwrite a file?

I have figured out to use totalcmd from the owncloud app.

Environment data

Android version: 2.15 downloaded today
Android 7.0