zoho creator funnctions stop to work on edit mode

Hi evreybody, i've this problem.
I was changing deluge scripting when i discovered that if i open the main form in edit mode, some functions about the relative sub-form stopped to work...but i can't understand why!
As you can see in the attach, i try, just for example, to get an alert from the subform, when entering a new description...if i'm in "on Add" situation, i got the alert correctly, If in "on Edit" situation, it doesn't work...could you help me!?!?!?

Thank you