Turns out this was caused by a couple of probes stuck inside the cube. Moving those out caused the lighting to look correct. The reason that it was changing with the camera movement was that one of the lights was shadowmasked. This means that it uses realtime lighting and shadows when rendered up close, but when rendering from a distance it approximates incident shadows by using occlusion values stored with the probes. So since there were probes inside the object and these were flagged as being in shadow, the cube was rendered as partially shadowed and thus tured out appearing darker than it should.