It's an issue with Joomla 3.6.0... Should be fixed in 3.6.1

See this PR for it: #11093

Thanks for Info

Closing

This issue is not just the redirect problem, i am using joomla 3.6 with VirtueMart 3.0.14, when user logout along with the wrong redirection the session of the user is also removed which causes the cart data of the user to be lost.
The redirection issue is due to the UsersControllerUser line 165
`if (is_numeric($return))
{

}
$return is string URL so the condition is false
you can add a else condition like
else
$app->redirect(JRoute::_($return, true));`
This will fix the redirection issue but the session management is still a problem.
Please fix the issue in J3.6.1.

You better talk with Virtuemart.
Since the correction brought to JUri::isInternal(), $return has to obey to some strict formatting.
The correction was done for security reasons.

The else condition is

        else
        {
            // Don't redirect to an external URL.
            if (!JUri::isInternal($data['return']))
            {
                $data['return'] = '';
            }
        }