Force Teamviewer to use Wifi

Y0gi

Hi !

I have a problem. I want to help someone to setup his router. He has a working wifi over a hotspot and teamviewer works.

But as soon as he connects his ethernet cable to the router, even though there is no internet connection, teamviewer uses ethernet and the teamviewer session stops.

So how can I force teamviewer to use the wifi connection and not the ethernet connection?

Thanks for any help

Greets