Looking at the aircraft’s flight history it did a couple of hops in the previous few days. Three flights within 24 hours wouldnt be unusual. The cabin pressure management system involves multiple sensors. These are monitored continuously. There is robust false-alarm rejection because you don’t want the oxygen masks dropping due to a false alarm.
If there is a warning indicator in the cockpit then one or more sensors is reporting that it is reading low, but not low enough to trigger the O2 masks, so probably around 9 psig. The pilots wouldn’t do any deeper diagnostics but I expect they called it in to maintenance. I expect maintenance assumed a faulty sensor and gave the listed guidance from the manual. I wouldn’t expect maintenance to presume the structure was about to fail (if you hear hoofbeats, think horses not zebras and all that). Sensors go bad much more often than doors failing in flight. If I got a call about a pressure warning I’d presume a bad sensor 99/100 times, but verify it upon landing.
