Accepted meeting invite sending new invite from them

Hi everyone, 

I have set up monthly Outlook meetings with a group of attendees. Often, I need to update the attendee list. When I do this, a few things happen:

1. I no longer receive a "Send to new attendees only" pop-up and the meeting invite is sent to everyone. It appears this is a problem with the new Outlook that does not have a resolution. 

2. Occasionally, when a user "Accepts" the meeting invitation, it sends a meeting invite to a subset of the meeting participants on their behalf. It is as if they created a new invite, but the report just accepted the meeting invitation. This has happened more than once with different people. 

Would love feedback on resolving this issue so meeting participants are not confused. 

Thanks in advance!