Quite the tale. So you have a WAN with some subnet of public IP, 10 WG tunnels, EoIP using WG peers. No BGP? e.g. just a subnet of public IPv4 on some bridge & using VRRP to potentially move one/more to another router on same “WAN bridge”? And all was working until you added a VRRP to WAN side?
Some diagram would help here for sure.
Your case is bit similar to one involving route rules and WG’s heart beat, where WG’s heart[beat] follows it own beat. See http://forum.mikrotik.com/t/wireguard-multi-wan-policy-routing/174145/1