Downloading a feedback set with groups when users hasn't got a group gives an error message the first time

Hi,

When a user with no group try to download a feedback activity set up for groups, it gives an error message:

These are the details:
You've already completed this activity.
Error code: this_feedback_is_already_submitted

• line 200 of /mod/feedback/classes/external.php: moodle_exception thrown
• line 550 of /mod/feedback/classes/external.php: call to mod_feedback_external::validate_feedback_access()
• line ? of unknownfile: call to mod_feedback_external::launch_feedback()
• line 251 of /lib/external/classes/external_api.php: call to call_user_func_array()
• line 550 of /admin/tool/mobile/classes/external.php: call to core_external\external_api::call_external_function()
• line ? of unknownfile: call to tool_mobile\external::call_external_functions()
• line 1496 of /webservice/lib.php: call to call_user_func_array()
• line 1342 of /webservice/lib.php: call to webservice_base_server->execute()
• line 44 of /webservice/rest/server.php: call to webservice_base_server->run()

Thanks for your time!
Isabel