Thanks Chris. Gemini Hand Controller reports target unreachable... But it's plenty reachable. I grabbed the laptop, went out there, got the same error on EKOS and this on controller, reset Gemini, reconnected, slews fine.
Thing is, I'd already tried this and it didn't do the trick. What would force the Gemini to think that the target wasn't reachable if I'd plate solved at that area and it "knew" that it was okay to slew? It wouldn't even slew to a spot close to the pole!