I can't say that I have noticed this before the latest update? (Vehicle Count = 3 but, on the same screen, you can see that there are actually 4 vehicles in the formation).
And another one. (By the way I am having some issues with the PCAs in general. 3 system crashes so far with copying appearing to be an issue). Will keep playing
UPDATE - Change that to about 20 x system crashes all created by me trying to make a formation of 6 x PCAs. No system crashes with any other wagon so far. I would like to say it is the copying that is the problem, possibly the system might be reading things as if I am adding a formation to itself, but nothing seems to be sticking with this wagon. Anyone else able to do anything with it?