My last 3 trips to the US with UA connections - one out via LAX ex DFW, one via SFO ex SEA and one via IAH ex DFW - I haven't had my boarding pass re-printed on these three trips- on each occasion the check-in machine directed me to a UA agent who scanned my passport and tapped a few keys and printed out my internal US, NZ international and NZ domestic boarding passes and all three worked all the way through. I wasn't called up to the desk and they scanned fine. I definitely was last year - not 100% sure when it stopped.
Sorry off topic with the ORD thread - but relevant to comments above