Range selection full vertical In one of my projects

In one of my projects whenever I use the range tool, the selection automatically entends to full vertical, without using the modifier keys. I’m not aware that there is a project specific setting that could cause that. In other projects this behavior doesn’t occur.
This renders the range tool useless in this project.
The project was started with Cubase 9.5 pro which recently was upgraded to Cubase 11 pro, and after a few times of saving the project the range tool behavior changed.
I’d be grateful for any useful suggestion to make the range tool useful again.

I’ve found the answer.
Per default, all my audio tracks reside within an “Audio Tracks” folder.
In the controls of this folder the “Group editing” button was engaged (I assume I did that unintentionally), which changes the behavior of the various selection tools.