Xamarin: object must implement IConvertible

Question

I get the following Exception

System.InvalidCastException: 'Object must implement IConvertible.'

on line 2, or any line after the start of the function.

public int SaveItem<T>(T item) where T : IBusinessEntity, new() {
    if (database.Table<T>().FirstOrDefault(x => x.ID == item.ID) != null)
    {
        database.Update(item);
        return item.ID.Value;
    }
    else
    {
        return database.Insert(item);
    }
}

Its being called by

public void SaveCategory(Category c){
     db.SaveItem<Category>(c);
}

The Function has been used for the last 3 years without a problem but when I recently had to update some NuGet Packages (namely SQLite PCL) it stopped working. Im at my wits end.