InfoPath Dev

I am having a very strange thing going on. Environment is O365, Infopath 2013. I have an Form Library that upon Submit, Queries the last ID of the form library (using a data connect called Retrieve IDs (does not auto retrieve data when is form is opened to avoid dupes), however, my users are not getting the same results. I keep seeing duplicates (the form is emailed so I am bcc'd on the email and see the form number to the vendor). However, when I go to the Form Library, either one of the forms is not in there OR they are both missing. This has me scratching my head. My first thought is that somehow one form is overwriting another. But again, I go back and and test it and it picks up the next number with no issues. I do plan on talking to some of the individuals who have placed forms where we have had an issue to see what they did and see if I can possibly reproduce issue while working with them, but at the moment, totally stumped. Any help or thoughts would be appreciated.

 Oh how frustrating. My guess would be that if the ID isn't getting correctly generated that you are having overwrites. And you are doing this on submit, so it does seems like you should be getting this number correctly (sometimes people do this sort of thing on form load, so you can see how that might cause an accidental case where multiple forms have the same id). Can you create a test user so you can try the form as a different account & see if you get a different result? And the both missing thing is just .... weird, right? You'd expect to see at least one of the forms there.... Are the users "helping" & deleting forms?