At this stage there aren't very many components on the board, so verifying you got orientations etc right shouldn't be hard.

Yeah, that's why I'm flummoxed. Everything looks perfect, including L1. The only components that I don't see nice clean soldering on the bottom (and the hole filled nicely with solder to the top side of the board) are the three caps, since they're sitting flush with the PCB. I think I'll try raising those caps to give a bit of breathing room... maybe one of those joins isn't done well, or maybe there's a bit of excess solder that flowed through the holes under the caps, making a bridge.