XR500 IPTV interupting xbox

I recently direct connected my XR500 from my ISP's Router/Modem to the Fiber node. ISP said that it's possible but i still need my OG Router/Modem for coaxial Moca. After a quick switch and enabling IGMP i was good to go with using port 1 for set top box and port 4 for Router/Modem moca box. after a few matches of PUBG and any online Xbox game i noticed 10-20 minutes LAN connection drop and immediatly resume requiring to sign back in but lose in match and basically not being able to play. After some tinkering i noticed if i disconnect port 4 Moca Router/Modem the problem goes away but no Fiber tv in the house. Any suggestions would help. I believe there is a better way toset it up i'm just not thinking of it as well.

Thanks in advance.