DHCP relay across sites

Hi,

We have a site connected to another via IPIP tunnel with a /30. I have tried to setup a dhcp helper/relay and doesn’t appear to work.
ROS v5.21

site1-10.4.8.0/24
|
tunnel
|
site2-10.4.2.0/24

The dhcp server is setup in site 2 and

the relay is configured as follows:
/ip dhcp-relay add dhcp-server=10.4.2.1 disabled=no interface=ether1 local-address=10.4.8.254 name=relay1

doing a torch reveals and the DHCP offer has a dst address of the tunnel interface and not the LAN. It’s almost as if the dhcp relay is natting the request with the wrong IP ? could anyone shed some light on this for me