Just recently installed 3.0.2 on Windows 10 64-bit. The theme it defaults to when I open a service, is not the default theme. It also is not the theme I saved the service with. It is the first theme I used is a service after I installed 3.0.2. I need to set the theme every time I open a service. This was not a problem in the 2.x version.
I have observed this as well. Very inconvenient. I've noticed that the theme nominated for the service may be 'ignored' (when it is the wrong one) and the theme I actually selected and saved is still used. Very strange.
Did you check the theme settings in the settings?