Violation of PRIMARY KEY constraint when published on Azure

ASP yields a Violation of PRIMARY KEY constraint on a specific ID. (I randomly generate the ID's in code, while checking they don't already exist in the database).

When I debug this code on my local machine (with the same Azure hosted database) everything works fine. When I publish my code on Azure I get the error. Strange thing is that the random ID, yielded by the error, does NOT exist in my database.

Code (I copy a list of medication with a new id & new schemeID):

        List<medication> l = db.medication.AsNoTracking().Where(x => x.scheme_ID == schemeID).ToList();
            foreach (medication m in l) {
                int id = generateUniqueMedicationID();
                m.ID = id;
                m.scheme_ID = newSchemeID;
                db.medication.Add(m);
            }
        db.SaveChanges();

generateUniqueMedicationID() method:

    private int generateUniqueMedicationID()
    {
        bool stop = true;
        int id = -1;
        while (stop)
        {
            Random r = new Random();
            id = r.Next(100000000, 1000000000);
            if (!db.medication.Any(o => o.ID == id)) stop = false;
        }
        return id;
    }