If the MPLS is your primary then it is expected behavior for the MX to try and attempt to form a tunnel over it. I don't believe there will be an option to disable autoVPN tunnel over a Primary uplink. You can enable Active-Active to have a "quicker...

Hey there, Is your MPLS link your primary or secondary uplink for the MX? And do you have Active-Active Enabled? That may explain the behavior your seeing. If you'd like to have a failover scenario, then follow this KBhttps://documentation.meraki.com...