^tried exactly the same tyre / rim combination (conti gatorskin on open sports) and am getting exactly the same problem. One part of the tyre sits too low. I suspect the problem is actually the rim as when I built the wheel it had a vertical dip near the join that was impossible to correct. Annoyingly, if I wanted to return the rim I'd have to take the whole wheel apart.
^tried exactly the same tyre / rim combination (conti gatorskin on open sports) and am getting exactly the same problem. One part of the tyre sits too low. I suspect the problem is actually the rim as when I built the wheel it had a vertical dip near the join that was impossible to correct. Annoyingly, if I wanted to return the rim I'd have to take the whole wheel apart.