Error in detecting WAN public IP in Dual WAN setup

[ibbetsion]

I have a dual WAN setup and am trying to have both of the WAN IP's link to a dynamic DNS domain at Google Domains. WAN1 is fine but WAN2 has the following error:

There was an error trying to determine the public IP for interface - opt1

Not sure why this is happening. If I disable WAN1, then WAN2 will update ok. Or when I reboot and WAN2 connects first, it updates ok but then once WAN1 comes online, WAN2 will not update with the error shown above.

Any ideas are appreciated.