Webform duplicate entry on edit
I've never had this problem and I use Webform in pretty much every project.

I would suggest your problem is based on the fact you're using a dev version of the module. Webform has a stable release of 7.x-3.18 whereas you're using 7.x-3.17+3-dev. The first thing I'd do is upgrade to the stable version, clear the caches, and see if the problem persists.

If it does, or you want to stick with the dev version for whatever reason, then you should report any problems to the module issue queue in the first instance.