Responding to your question and a few other points for clarity:
For the door, unfortunately Ana was not able to unlock it immediately either. She only opened it after trying the 'trick' I mentioned: "lift the whole door upwards with your body while simultaneously wiggling the key to a secondary click". She mentioned that to prevent this from happening we should not lock the door from the outside when we leave, but we weren't given that information before. I think that is helpful for guests to know ahead of time to prevent the hassle for everyone.
As for 'Europeans' not having trouble with the doors, I have spent a lot of time in Europe and haven't had any issues with doors before. Just your door. And it was because I needed specific instructions that I wasn't given.
Maybe you could create a 'house info' sheet for your guests? Most places I have stayed at do this and it helps.
For the late check-in, we were at the door to the apartment at 9:20pm, not "after 10pm", and regardless, you said the extra fee applies after 8pm so I thought that would be helpful for other users to know as they plan.
Overall your place is lovely and these are small things. Hope the feedback helps make things smoother for everyone moving forward.