I don't think Adobe goes into great detail about how their system handles the data...
Now, when you say "multiple broswer and os" I am hoping you mean based on updates... like the user updated their OS to the last version, and their browsers get constant updates... (not like you are seeing the same user going from iOS to Android?)
Mobile ID should be unique for the device.. I cannot understand why that would change... is it possible that your implementation is somehow forcing user identifications into the tracking strings (aid, vid, vidn should be set by Adobe processes.. but it's possible that someone trying to be clever could be manipulating these and causing some data corruption??)
How different are the values you are seeing, and how many users are impacted?