Hi!
I looked at it this morning and it’s working for me. The “2 years” button is the one that places focus on itself, and that one does remove focus from the field. I’m on a mac using Chrome. I don’t have a Windows machine so I can’t test it there.
Interesting tidbit: when I try it using Safari, everything works as expected on all buttons, so this seems to be a bug using Chrome only.
If you are still having problems, try this: give the button a focus style-effect that actually changes the appearance of the button when I gets focus. If the appearance of the button changes, and the field still has focus, that would be amazingly strange. [Edit: Disregard the previous comment, as the selection style supersedes the focus style.]
Good luck, and let me know how things work out!