Whenever I go Marketing> Contacts>  and click Lists. Once I select the list I want to add the contacts to and click "Add Contacts" the page just continually reloads. Note this only happens when adding the first contact to the list. After that it functions normally. I have found a work around by finding the contact first and then assigning them to a list instead, but it might be something worth looking into.I have tried 2 different browsers Chrome and Firefox and still have the same issue.