Sorry to hear that especially after all the work of the rebuild.
I had a friend with a very similar failure - looked like a slipped sleeve (#6) on a '99 with under 100k miles on it. Pic is from the guy that bought it afterward when he had the engine torn down:
I had sold him the car about a year earlier thinking that the engine was in great shape and that by the age and mileage it was past the chance of having the 'early Boxster' failure modes.