Mobile menu is to short on highend

Hi guys

I have found a problem with the last item in a menu in the drop down list on my site when shown on a mobile menu. I have 9 options in my menu ( I had contact us as the last item on the right in the menu but I moved contat me to the left for now so Charities is now the issue on my mobile). Any item thats the last item will do the same. the menu will allow you to click on any item in the drop down list except the bottom one, it keeps hiding when you try to sellect it. any ideas how I can fix it.

Thanks