You too had a dramatically increased build-time? I've been messing with 2D lights already, maybe I can help figure it out.
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I think the problem I had was with an animator. I had placed a 2d light with the intensity turned to 0 on an object, then used an animation to ramp the intensity up when triggered. It caused a couple of objects to spawn in weird locations. I think perhaps it was resetting the transform location even though the location was never animated? Like I say, weird last-minute problems, heh. Fortunately removing that effect fixed the problem...