conditional calculation is not working

I am trying to create conditional formatting relating to an age. If over this age, calculate x into drop down menu1, If over a different age, calculate y into dropdown menu2. I have a birthday input field and I have the calculations set to work, but when you are inputing the birthday it resets the dropdown menus to blanks. IF the date calculated the age to over one of my 2 limits then it behaves properly, but if not, it resets the menus to blank and you have to re-enter the information. Is there something I can add where if age is under x or y then do nothing or have the dropdown menus default to the last choice instead of blank?   

I have checked your form and replicated the issue.

It seems that the form calculation is not getting the string function.

Kindly input again the values in string.

Here is a sample screen cast:

Please give it a try and let us know how it goes.

Thank you.