BUG with function get_upload_user_base_dir

Hi,

I get this error after no real changes to my site.
I am using default theme since I am still building the site.
I did a conflict test and only UM is active.

Still the error persists

Recoverable fatal error: Object of class WP_Error could not be converted to string in /home/europeanmoving/public_html/skills_site/wp-content/plugins/ultimate-member/includes/core/class-uploader.php on line 204

It happens when I try to register new user with custom made registration form.