Image upload: Failed to open output stream I created a media entity browser and for the image upload widget i choose the DropzoneJS.The widget settings are in the image bellow, pretty standard.



And regardless of image type (png, jpg, jpeg) any image selected for upload returns with the follow error message "Failed to open output stream". I'm guessing the upload is ok but it can't be saved?

The public dir is writable (sites/default/files). This is tested successfully when for the widget type i choose normal file upload. The image is uploaded and saved successfully.

Dropzone lib is the most current one from their master branch on GIT (was previously on 4.0.1 but i thought that the version is outdated and that was causing the issue, i was wrong).

Core: 8.5

Any ideas?
In /admin/config/media/file-system look at the value of "Temporary directory" (/var/tmp or /tmp or ...) and check if that path is writable by the webserver user.