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When a user opens a form, goes to step 2 and quits (for whatever reason he does not have time to coplete your survey or other form)
if the form then changes, for example step 2 is removed and all values are added to step 1
the user returns to the form, and will see an empty step with a next and a previous button (whiech both lead to page not found errors)
there is no way for the user to go back to step 1 or start the form all over again. except for maybe removing his cookies and history
this could be changed as in:
first check if such step 2 actually exists, if not render the form from scratch.