I have found an oil field that contains a well that cannot be harvested because all possible output sides for a pumpjack are blocked by other pumpjacks. https://i.imgur.com/C5k3V3L.mp4
I was going to make a bug report, but I realized that I have RSO installed. It's possible that vanilla Factorio would have prevented wells from spawning like this, but RSO overrides that behaviour. I don't know if any of that is true, though, hence my question.