When adding tabs (through .tabs('add')) to an exsisting div element the class ui-tabs-panel is not applied, although this calss will be applied when creating tabs from the init. The below code fixed this for me

            // try to find an existing element before creating a new one
            var $panel = $('#' + id);
            if (!$panel.length) {
                $panel = $(o.panelTemplate).attr('id', id)
                    .addClass(o.panelClass).addClass(o.hideClass);
                $panel.data('destroy.tabs', true);
            }else{ // Ensure styling is applied to exsisting tab element
	       $panel.hasClass(o.panelClass) || $panel.addClass(o.panelClass)
			}