Mac has multiple draft emails with Gmail on Server

PLEASE ACCEPT MY APOLOGIES FOR POSTING THIS AGAIN, but despite my request for assistance and not to pollute the thread, that is exactly what happened to my original post. Please accept my apologies for the duplication.

I am using Apple Mail with a Gmail account on my iMac, iPhone, iPad and, sometimes, through a browser.

When replying to an email message, Apple Mail stores multiple (sometimes 100's) of versions of the draft email and *DOES NOT DELETE THEM* when the message is sent. Apple mail is configured to keep drafts on the server, which is what I want to happen, so that I can sometimes finish them on other devices. This behaviour is NOT present when using any other device, so the bug is specific to Apple Mail on Mac, (not iPhone or iPad).

Reproduction steps are easy. In Apple mail on an account connected to Gmail, open an email that I've received, and start a reply, continue typing occasionally for say 5 minutes. Then send the mail. Now search for it in Apple mail. I will see about 5 versions of the mail on the thread (I have "organise by conversation" setting on). Viewing the same account directly in Gmail web interface shows the conversation with drafts, and the last version open as if unsent.

I know this issue has been raised before, but it has incorrectly been marked as solved, so I am raising it again in the hope that it can really be solved this time. (For background, the action previously incorrectly adopted as a solution is to configure Apple Mail to not store drafts on the server. This does not solve the problem as, although you don't then get multiple drafts, on your other devices you don't get a draft at all! So, that's not a server-based email system.)

This behaviour is present regardless of the mail account type used - using the recommended 'Google' account type or using a general IMAP account to connect to the Gmail service each exhibit the same bug.

This bug has been present for a number of years and OS X versions. It is about time it was addressed. If anyone has a fix for this please respond here. Once again, I ask politely that this thread is not polluted with "solutions" of "don't store drafts on the server", since that alternate behaviour is well documented and discussed elsewhere on this forum. I know many other people are frustrated at this behaviour and I am posting this again in the hope that something useful (rather than just being told I am wrong) will result.

Thanks

~Joe

iMac - Sierra / Apple Mail / Gmail account