Somebody on the RR.net Type 9 tracker thread phoned up "someone in the know" and said there was a minor mechanical issue that got them all yanked for a couple weeks, which has now been fully corrected. The fleet is still under warranty break-in period despite 23-of-24 units being accepted for revenue service, so I'm guessing that even if it was an extremely trivial issue they still needed CAF techs to fly in for a site visit to poke under the hood before enacting the fix. Their absence was barely noticed by the riding public because the Lechmere-end shutdown, B shutdown, and quiet Memorial Day Weekend meant so many fewer trainsets have been on-rotation this month in the first place.Good news: a pair (edit: Transitmatters' New Train Tracker says two pairs!) of type 9's were running today. Whatever issue was present that kept them from running in two-car trains seems to have been resolved.