Text in edit field disappears after opening substack.

[Charles Szasz]

I am using LC 5.5.5.  I have a substack ("Grade") that is launched when the user goes from an edit field to the next edit field. The substack has a grade option button that is programmed to insert a grade in the second field. I have no script in the first field. When the substack is launched the text in the first field disappears. 

This is my script in the second field:

On openfield
If field "grade2" is empty
 then
  go stack "grade"
end if
End openField

Has anybody run into this problem?  Does anybody has a solution to this problem?

Sent from my iPhone 4S!