Comment # 5 on bug 1106993 from Martin Wilck

Today, after booting, the phenomena described above didn't occur. This time NM
correctly associated the devices with it's configured connections
("wired_dhcp", "vlan-vlan10", "vlan-vlan20" below, and no problems were
observed.

> mwilck@apollon:~> nmcli con
> NAME                   UUID                                  TYPE      DEVICE    
> virbr0                 878efa52-0744-409d-bc11-b3c2a642ec23  bridge    virbr0    
> virbr1                 067f0505-e56c-4441-b0b4-faa07d5780a2  bridge    virbr1    
> vlan-vlan10            9fdf61c7-a18c-415e-a02a-e9d804ef08a6  vlan      vlan10    
< vlan-vlan20            cc771a2d-f01a-461c-a1b8-1c5118a14c9e  vlan      vlan20 
> wired_dhcp             b99bd77c-b92a-453d-a714-fef71dfd5586  ethernet  enp0s31f6 
> bridge-br0             e1557585-b953-49f9-9b8e-fafd66e4e49e  bridge    br0       

Thus this seems to be sporadic.