Updating script. . . never ends

Updating script. . . never ends

What does this mean when trying to update a script?  

Specifically, I am updating a form script on edit / on success.

When I try and navigate away from the screen it warns that I will lose changes and indeed they are lost.  I am trying to isolate the offending line, but it is difficult because of dependencies between different lines re. referenced variables.

Regards . . .