Duplicate cases created in Headquarters

In several different data sets that we collected using Survey Solutions over the last few years, we have noticed that the data sets we download after the data collection is complete have a few new duplicate cases. In all of these instances, the original samples that we uploaded to the server had no duplicates, but the final data set does have some duplicate cases. Is there a possibility that the supervisors some how created copies of pre-loaded sample cases? If not, is there anything else that could explain this phenomenon?
Thanks in advance.

Yes, it is possible.
Please check the support site, it has an article explaining how this may happen.