JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
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It appears that you have already reverted to Form Builder V3. You can also change this option on your end at any time by going to Account > Settings > then checking the form builder version you want to use.
Can you please provide us with information on how the form builder crashed? It would help us if you can give us some steps on how to replicate the issue where the form builder crashed. That way, we can send a report to our developers so this issue can be fixed.
Please let us know if you need further assistance.