Actually VLAN ID 1 is no different than others. If everything is configured correctly, also VLAN 1 should work just fine. But there’s a gotcha: VLAN ID 1 is used as default all over the place, it is not shown in output of export (since it’s default) - unless export is run with verbose option. So it’s really easy to miss some VLAN ID 1 setting somewhere where it should not be and sometimes it’s hard to get rid of that setting as well. Hence the easiest way of not getting into trouble is to stay away from using VLAN ID 1.