If you know an airline/pipeline/etc.. engineer who could tell you the proper methods I am certain that you can, if you are correctly certified, make these welds with no adverse affects (or at least the engineer could tell you how to counter them).... otherwise, I would stick with the manufactured ones...
Might I suggest photoing and sending the photos or returning the rim directly to the manufacturer with a note stating that you believe this is a manufacturing defect (a potentially hazardous one).... My bet is that they send you a brand new one post haste.... they hate that kind of thing and most companies are very generous about helping in issues where there merchandise might be suspect...
It won't get you out of your jam, but it will probably land you a new rim....