Couldn't remove interface veth but no container exists

[admin@RouterOS-home] /interface/veth> remove 0
failure: in use by container
[admin@RouterOS-home] /interface/veth> /con
console     container   
[admin@RouterOS-home] /interface/veth> /container
[admin@RouterOS-home] /container> pr

[admin@RouterOS-home] /container> /int vet
[admin@RouterOS-home] /interface/veth> pr
Flags: R - RUNNING
Columns: NAME, MAC-ADDRESS, CONTAINER-MAC-ADDRESS, DHCP, ADDRESS, GATEWAY
#   NAME           MAC-ADDRESS        CONTAINER-MAC-ADDRESS  DHCP  ADDRESS         GATEWAY   
0 R veth-smartdns  4E:06:65:25:82:59  00:00:00:00:00:00      no    10.20.3.171/24  10.20.3.96

Try to reboot the router if you haven't done it. Otherwise, follow this instruction to export your configuration: Forum rules - #5 by gigabyte091.