Team Viewer very slow

I am having extremely slow speed when using Team Viewer 14.

The devices that are connecting to eachother both have 400+ Mbps download and 100Mbps upload. They both have very good hardware, one of which has hardware that is pretty much the best you can buy. Teamviewer is aloud through all firewalls. 

I have tried using the view option to "optomize speed"  and have also tried messing with settings myself in the "Custom settings" to slide the quality to "highest speed" and turning all features off (including hide desktop) and it barley makes a difference. 

Viewing video or listning to audio of any kind is a joke, and even jsut trying to use the desktop or web browser is also laughable. They are incredibly slow. Everytime I research what to do all I see is your internet is too slow, or adjust the custom settings. My speed is more than enough, and custom settings are where they should be, so what now ? 

How can I make this connection faster ? Or can I ? I have people that use the same internet connections and there's run absolutely fine, some even have PC's with lower specs then mine, and lower internet connections. There is no reason it should run this bad, but it continues to without fail. 

If anyone has any ideas in what to do, or change, or try please let me know.