My guess is still something aft of frame 57 (or whichever frame separates the Ops compartment from the RC on a hotel). If not an outright ORSE failure, NRRO is most definately involved.
I had a skipper once that made Queeg look like the second coming of Mush Morton. But we always managed at least a SAT on ORSE and TRE is all was good.
If in fact that were the case, there would have been a lot more people going away, not just the CO. Something tells me it might actually be worse than an SBA on ORSE. I’ve seen CO’s who have failed (or SBA’ed) one, got a BA on the next, and still managed to keep their commands.