Ive tried the config on both WAN1 and WAN2 with the same result. I've done some more testing today and I can use exactly the same hardware Draytek 130/mx84 on a different provider VDSL connection (Zen) but the combination of MX & provider Vodafone does not seem to work.
Just to breakdown what I've tested.
Vodafone provider
MX & Draytek 130 (doesn't work)
MX & BT Openreach modem (doesn't work)
Draytek 2860 router (works)
Sonicwall with with Draytek or BT modem (works)
Zen provider
MX & Draytek 130 modem (works)
Sonicwall & Draytek 130 (works)
Draytek 2860 router (works)
So to me it seems like something directly related to the Vodafone provider and MX, the only thing that's obvious to me is that in the pppoe username for vodafone there is a hyphen and I'm not sure is this is causing some issue with the MX or not. I won't lie but the support from Meraki on this has been poor and at the moment I've got a £3k door stop.