>I live and work in a multi-lingual environment, and regularly switch between the German and English keyboard layout. Lately, the keyboard layout no longer sticks. It resets to English when I press shift. Sometimes it does work, sometimes it doesn't.

Yeah, windows is also the king for that.

Almost every update reactivates the shortcut to change locale, even though I've removed it.

And they even added a new shortcut to change locale : Win+space.

So as I'm always juggling between mac and windows, Win+space is sometimes pressed instead of ctrl+space and then all of a sudden my keyboard is switched to another language.

Don't worry, there's a fix ! Modify all the installed language, add your keyboard layout and remove all the others. So now you can also have a an English locale with a non English keyboard layout.