028 is in service this morning, and there's a 150 parked up in the bay platform at Pontypridd which will presumably take over operations in the afternoon.
022 and 030 are the units out on test.
There was a claim made a few pages back in this thread (post 2028 onwards) that the 398s have clocked up 5,000 miles of trouble-free running, and some discussion over whether this was actually the case or was a requirement that hadn't yet been achieved.
Can we assume from your post that unit 028 has achieved that milestone, and the other two haven't yet?
Does a fault on a unit reset the "trouble-free running" counter to zero? Or is it cumulative between faults (which I find difficult to get my head around)?