Ethenet 10gb stop working when wifi connect/disconnect

Your Mac is surprisingly smart about some networking things, and surprisingly stupid about others.

Packets going toward the internet are sent to the TOPMOST, Working interface in

Settings > Network

all others are sent over the paths through your connected networks that appear to have the lowest delays. In the past, an additional hop through another network node to get there, usually overwhelmed everything else, so it merely optimized for lowest number of hops. with 10G Ethernet available, I do not know if 'number of hops' alone is the determiner.

your computer does not necessarily do what you want it to do. You said you wanted the fastest connection going to your NAS, only. But if there is ANY other connection from there to the rest of your network, that may not be the route the traffic is taking.

it sounds like your network is too complicated, and despite your best intentions, contain an unintended cross connection between the subnets.

My recommendation would be to treat the 10G Ethernet as your Network backbone, and hang all the other devices off that backbone. The added traffic from internet connections would be truly negligible.

My home is a Wi-Fi dead zone, because of solid Masonry construction. I have added a four-port 10G switch with several 1G branches, and connected all other Routers and Wi-Fi access points (five including the Internet Router) to what is basically an Ethernet network that has a 10G core that connects my main computer to the main Server.

what interface is TOPMOST in

settings > network ??