Pop-up windows taller than the screen are too much to the left, not fully visible

Please always provide references to previous discussions about the very same topic in other venues, to not make people spend time having the same discussions again and again and again.

https://gitlab.gnome.org/GNOME/gnome-panel/issues/2
https://github.com/lafrech/qbirthday/issues/14
https://github.com/lafrech/qbirthday/issues/13
https://answers.launchpad.net/ubuntu/+question/669732

Thank you, Andre, for connecting the dots. Sorry, I did not provide the reference; I thought it is not relevant as it was dismissed to be a GNOME issue (https://gitlab.gnome.org/GNOME/gnome-panel/issues/2) and the developer could just confirm that it was working in MATE (https://github.com/lafrech/qbirthday/issues/14) which I stated in the description.
Thanks for working on this!

I've never seen this bug occur with any other app. I would guess it's most likely a bug in https://github.com/lafrech/qbirthday/issues/13 and not a gnome-shell bug.

However it might be a gnome-shell bug if there is something strange about the window that doesn't happen elsewhere. Can you please try moving the window into full view and then take a screenshot of it? You can move it by pressing Alt+F7, then drag and click.

Is the window taller than the screen?

Thank you, Daniel, for your helpful comments.

As once every other week, the window opens with one click and mostly visible (just a bit too much to the right), I thought it is more related to the gnome-shell or any other component of the system as to the app itself. The app is always started with the start-up of the computer.

Any other window so far is not displayed outside of the visible screen as far as I remember.
Yes, I can move the window after pressing Alt+F7 with clicking on it and dragging it to the center.

Your last question was the best! :) The window is indeed taller than the screen! I could reduce the list length (reduce the displayed birthdays in the preferences; why did I not try this before!?) so it would not be taller anymore and wow! the window is placed within the screen although to the far left but fully visible! Wonderful, this solves my problem I hope.
But I wonder why the window is not shown when it is taller - this was never a problem in the past (e.g. Unity) and why there are rare times the window is shown mostly visible (although to the right). Maybe we will never know but I hope the reduction of the window height will be a permanent workaround!
Thanks again for your helpful comments and questions!