wireguard/netifd: Second wireguard interfaces does not initialize correctly on reboot

On most restarts of the router, my second wireguard interface (see screenshot below) is not initialized properly. The interface does not work, RX/TX counters are at 0. Restarting the interface or the network does not fix the issue, if the interfaces does not come up after a reboot, you have to reboot the whole device and hope that it works this time - if not, reboot again. In most cases, it works after two or three reboots.

netifd logs look like the interface is up and running, but it is not:

Oct  6 10:54:48 GatewayDummi netifd: Interface 'vpn_wg1' is now down
Oct  6 10:54:48 GatewayDummi netifd: Interface 'vpn_wg1' is setting up now
Oct  6 10:54:49 GatewayDummi netifd: Interface 'vpn_wg0' is now down
Oct  6 10:54:49 GatewayDummi netifd: Interface 'vpn_wg0' is setting up now
Oct  6 10:54:49 GatewayDummi netifd: Interface 'vpn_wg1' is now up
Oct  6 10:54:49 GatewayDummi netifd: Network device 'vpn_wg1' link is up
Oct  6 10:54:49 GatewayDummi netifd: Interface 'vpn_wg0' is now up
Oct  6 10:54:49 GatewayDummi netifd: Network device 'vpn_wg0' link is up

Screenshot:

I need to use two wireguard interfaces because they have different routing tables. The first interface is for "normal" VPN access, the second is for policy-based routing (pbr). The wireguard issue is not related to pbr because it also happens when I disable pbr completely.

Start by reproducing the reboot failure with two WireGuard interfaces and inspect the provided netifd log sequence for vpn_wg0 and vpn_wg1. The issue names no source files or tests, so trace the interface setup path in netifd from those interface names. Done means both interfaces initialize reliably after reboot and their RX/TX counters work.