It you use RadarBox (or SBS) for long enough then sooner or later you will pick up a hex code being used by an aircraft different from the one that you first picked up using that code. Chances are it will be a US code, as they are frequently re-used, but it could be German, French, Bermudan, Israeli, etc.
Unfortunately both the RadarBox and SBS databases are designed around the assumption that hex codes will never be re-used, and so you can only have one set of aircraft details per hex code.
Short of capturing all your Mode S data to an external database and making the appropriate adjustments there, I don't know of any way around this problem.