With an older image there was a problem when the router / DHCP server was IPv6 capable. I thought that we'd fixed this on latest image but at least this would be worth a look and try. In case your router also takes care of IPv6 try to temporarely disable this, burn image again, boot and see what happens.
OMV will reboot itself one time automatically and this IPv6 bug led to no network after reboot due to screwed up /etc/network/interfaces file.
Thanks for the help. I will try this as I do believe the router had ipv6.
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