I received some boards back from the PCBA fab and noticed that one 0402 resistor is flipped onto its side (R25):
This site tells me this is a pick-and-place error. But the footprint happens to be one where I increased the space between the pads very slightly, so that I could run a trace in-between. Other instances of the same footprint were correctly assembled by the fab.
Question: is this defect always caused by an incorrect pick-and-place setup, or can it happen during reflow in a phenomenon akin to tombstoning?
In that case, could the modified footprint be responsible?