So I was trying to book a ticket MKE-IAH-AUS for this fall and noticed that the 39 minute connection is no longer allowed. The previous minimum connection time through there was 30 minutes, at least as of a couple months ago. When did this change? Has anyone else noticed this?

(ETA) Even stranger: The flights show up as a legal routing connection on both the UA and CO timetables. Both segments are wide open. Why won't any booking engine let me leave MKE at 5:40 on 10/15 and land in AUS at 10:05?