CardBook tab resizes Thunderbird window
This might be difficult to reproduce since it might be related to my layout and some other addon like Lightning. But basically, I set the Thunderbird window to a specific size but when I click the CardBook button, the width of the window gets increased. In the CardBook tab, I cannot decrease the width of the window. If I switch to the mail window or calendar window, I can decrease the width, but when I click the CardBook button, it gets increased again. So it seems like CardBook requires some minimum width. I don't remember CardBook behaving that way several versions ago.
My setup: Linux, Thunderbird 52.7.0 from Ubuntu, CardBook 31.3 (I don't know when this started but it also happened with the last few versions)