Errors in calculation on sheets when transfering?

Has anyone seen calculation quirks occur when someone uploads a character sheet to a game? The example is that I have someone who uploaded a sheet into my campaign (which is using the 5e OGL sheets).   His Dex is listed as 11, but the Initiative is calculating at +1, instead of 0.   I've seen similar things with weapon attacks being off by 1...I can't see anything in the sheet settings which is incorrect (I set the global initiative mod at -1 to compensate in the short term).    I will say that the player in question doesn't remember what sheet he used in the campaign he originally created the character.  This is an Adventure's League game, so we frequently use the upload character feature since players bounce around from table to table...but *most* of the other AL DMs use the OGL sheet.

Many sheets use Attributes with the same name, sometimes for different purposes. The existence of such conflicting Attributes on the Attributes & Abilities Tab of a Character can often cause unwanted behaviour. This can be fixed by identifying and deleting the conflicting Attributes. For example, the 5e Community and 5e OGL sheets both use Attributes named "<skill>_bonus", e.g. "deception_bonus". It's necessary to delete all such preexisting Attributes when using the 5e OGL sheet; otherwise, issues with skill modifiers will become evident.