I have tried this as well !Turn aero back on.
This might be the problem, i will try to download the newer version and see if the problem still exists !You are using an older version of OBS Studio, version 18.0.0. The Window class setting for Window Match Priority is not available in 19.0.2, at least in my drop down.
I would go download and use the current version 19.0.2. You should always be running the new version anyway.