Append "node" to tab menu link
This isn't a problem with the view. The url paths used for your tabs are using relative URLs (e.g. "node/$nid/group-forum") you need use absolute URLs (e.g. "/node/$nid/group-forum").

&lt;ul class="tabs--primary nav nav-pills"&gt;
  &lt;li class="active"&gt;&lt;a href="node/1147" title="View"&gt;&lt;i class="fa "&gt;&lt;/i&gt;View&lt;/a&gt;&lt;/li&gt;
  &lt;li class=""&gt;&lt;a href="node/1147/group-forum" title="Forum"&gt;&lt;i class="fa "&gt;&lt;/i&gt;Forum&lt;/a&gt;&lt;/li&gt;
  &lt;li class=""&gt;&lt;a href="node/1147/members" title="Members"&gt;&lt;i class="fa "&gt;&lt;/i&gt;Members&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;


You need to check the rendering logic in your theme templates to see where the problem lies.