Day selection does not work if started on top left calendar cell

When I switch to any future month (for example May 2017) and click on top left cell (1st of May) to start the selection, selection does not follow the mouse cursor and only one day remains selected. Problem is easy to reproduce on demo page, occurs in front-end display, shortcodes, widgets and on admin pages. Not sure what happens when “per night” calculation is enabled, but I think issue might be the same.

Anyway, thank you for great plugin!