It would be better to comment this but I only just joined, so no reputation...you'll also have to forgive me if this is a silly idea, I'm not a physicist :), it's just my 2c.
For the sake of argument, assume that (from the perspective of an observer on the "ground") the light deflection really is twice as large as the bagel's rate of fall - or at least different, since otherwise the question is moot. Then the most logical inference, to my mind, is that the contradiction is itself the answer. That is to say...
As <PERSON> has pointed out, you can't really get the "uniform field" we're imagining in the problem; so while from the bagel's perspective the light bounces back and forth between the mirrors, what an observer on the ground sees it this:
That is, mirrors that are perpendicular to each other from the bagel's perspective are not perpendicular to observer on the ground (because of the gravitational field), they're bent over slightly so that they're perpendicular to the path of the light, and the light bounces back and forth like a tennis ball. 562
Kind of like - the very phenomenon that causes the light to be deflected at twice the rate expected is the same one that causes this, and fixes the contradiction it introduced. So, the observer on the ground sees the light bouncing back and forth as illustrated in the figure, until the bagel and light hit the ground together.
The same kind of reasoning could apply to the variant with lots of bagels in a row. The bagels see themselves in a straight line with the light travelling straight through their centres; but an observer on the ground sees the bagels lying on a curve that accounts for half of the deflection of the light. When dropped, the observer sees the bagels all fall together, and the light going through all their centres - the extra deflection being accounted for by the fact that the bagels aren't in a straight line from his perspective.
Again, I'm not a physicist so I may have missed some important points (both here and in reading the first answer), but hopefully this makes a little sense. 562