Server 2016 msg problem.

Hello.

I have very strange problem with Server 2016 RDS Remote App.
Previously i used server 2012R2. And when i send message for user (msg command), they can easy click on OK button and close this message.

But a completely different situation with the server 2016. Users receive a message, but cannot press OK buttom. This message on background and block all windows. They need to press alt+tab combination and select remote app. And only after that they can press Ok buttom and unblock all other windows.

All clients have windows 10 1803

Any ideas how to fix this problem?