clone mac address

My router is the RT-BE88U. It is the main router in an aimesh. I was experiencing issues with my xfinity gateway in bridge mode and struggled with this for a week thinking the problem was on their end, but narrowed it down to what I believe is a bug in the WAN MAC clone feature in the router...

I've recently upgraded to Asus AC3100 from AC68U. Everything works fine but my IP address changed to a totally different one. It messed up with several services that I'm using. I'm wondering if there is a way to keep the old IP address? Thanks!