Additional VLAN interface cannot create to the port where the VLAN interface is set.
The following messages pop up.
The hardware you selected is in use by a VLAN interface. It can only be used to add additional VLAN interfaces.
I create additional VLAN interface in Network > Interfaces > Interfaces > New interface.
I think that there must not be mistake in the operation, because it was able to create at 7.201 without trouble.