The 171/2s and /4s (ie. ex-170s) haven't been causing too many problems for my journeys lately, but a lot of my colleagues have had quite bothersome issues. In fact, one failed on prep only this afternoon, which resulted in short formations. So I think my experiences are luck more than anything! Some things are accessibility or cosmetic issues - there's at least one unit going around with no PIS when driven from one end, some dodgy toilet doors and so on. Others have more serious problems - spurious fault lights, unsolicited brake applications, etc.
It's hard to know the exact root of some of these problems, but from the expert opinions I've heard, I would indeed agree that leaving them as 3 car trains might have improved reliability, if not practicality.
Depends on definition of a few weeks ago. There was a staged introduction of them last summer, and there were I think 3 or 4 am peak services that were 10 car, in the evening I think it was 5 peak services that were 10 car. Although regularly at least one of them was short.
However several weeks, if not months the alternate service on the Marsh line was cancelled though lack of stock. This was reinstated but the length of services on the Uckfield line reduced and there is only one train that runs as 10 carriages but does 2 journies am and pm well 1 1/2 in the am as it only goes back out as far as Oxted.
That Oxted shuttle in the morning is a bit silly, really. It often either gets stuck in congestion or causes its own, and only really serves much purpose on the way back into town between East Croydon and London Bridge. For some reason it has never really proved that popular as a crowd-busting train from Oxted.
The Down journey of that shuttle often only has 2 or 3 people alighting at Oxted, from 230 metres of train.
However, given nobody wants it to take up space by manoeuvring anywhere else, I can't see things changing any time soon!
From that video I can only see one ex Scottish 170 in that though. The rest appear to be made up of 171s.
They're all 171s now
But yes, often you will only have one ex-170 unit in the formation.
I saw a few in that video, but I was expecting most formations to have the extra units in them.
There's no consistent pattern, I'm afraid. It just depends what's functional on any given day!