Hello, Andrew.
It could be some device on VLAN 1 that is using the same router id as the one you are monitoring.
How was router-id assigned to your router - automatically or manually?
Check current router ID and review all the neighbors: they could be using the same IP-address (id).
One more possible reason is that some device in VL1 is forwarding you back your OSPF Hellows.
You might try to capture ospf packets (just connect any workstation to VL1 in promiscuous mode and use Wireshark) to see source address and content.