Strange operation of actionscript

I am building a program for my little boy that requires him to answer simple mathematical problems.

The first frame requires him to answer addition problems, the second frame requires him to answer questions on subtraction.

If he passes through the addition section the second frame still functions as though it is addition BUT if i program a button to go straight to the subtraction frame it works correctly as subtraction.

Any ideas on this.

Help would be greatly appreciated.

Rod