Mail app issue with gmail

I have a very frustrating issue with mail app. I am using the mail app for my gmail email address.

The issue is that, when I am writing a new message and would like to save a draft, the app creates a NEW draft for each time I press cmd+S to save the draft state. So, by the time I finish writing the email, I can see 20+ new drafts all sourced from the single message.

I experience this only with mail app. I used another apps, and all did not have this issue.

I am running osx yosemite.