Visible map size

Hello.
Is this block with map – is hidden when document is loading?

Yes, it is located inside a tab that you need to click on to display it

Hello.
So, you need to re-call init functions after you show your map, as google try to draw only visible parts, and when document is ready – map is not visible on your site. You can get some ideas from this topic https://stackoverflow.com/questions/4064275/how-to-deal-with-google-map-inside-of-a-hidden-div-updated-picture (exactly your issue on screenshot) and this one https://stackoverflow.com/questions/7084363/google-maps-in-hidden-div

Thank you for your help.