Really? That is a pretty poor set of excuses. A whole new end could have been fabricated for each coach by now with ease. This is fairly straight forward fabrication work. We have companies in the UK that can build entire power stations quicker than Wabtec can fit a few doors.
i accept that a bit of time would be taken at the start to get the methodology sorted, but if Wabtec are really trying to say there programme is over a year adrift because they didn't think or allow for 40 year old coaches having corrosion, or not being perfectly manufactured is really risible. That excuse would hold water for a wee while but is now way past its sell by date.
There are perfectly reasonable questions to be asked as to why 4 months after the firs tone was delivered we have not seen a second set. At this create the delivery programme will be likely to be around 10 years. That would mean better looking at other options.
The methodology of fabricating new coach ends was very well understood - that was how the plug doors were installed on the Chiltern Mk3s - but that also took far longer than initially expected, because as EE Andy b1 has indicated, in effect no two Mk3 bodyshells are the same - taking the end off was easy enough, but it was then a hell of a job to get the new one to line up with the rest of the bodyshell and attach it.
The idea behind the plug doors was that you took that problem out of the equation, but unfortunately the 'quicker and easier' method has turned out not to be.
Since the first Scotrail set was delivered, Wabtec have completed a seven-coach set for XC and the second GWR four-coach set, plus a spare coach for GWR - which I assume was in line with the promised delivery programme for the three TOCs. Hopefully the pace will pick up, but who knows?