There is nothing in new models as far as "reproductions" being comparable to the real thing with it's original fabric ( regardless of condition) , and while the "real thing" has it's own issues due to age and condition, I think an error was made in creating these more complex electronic hybrids, which are not really reproductions unless you do not look past the shell. To call them reproductions is stretching the meaning of the word, as if you bought a 1928 Ford with a 2012 hybrid engine. These "toys' are in a class by themselves and to call them tinplate is also a bit of a stretch, unless you define it by style rather than what the originals actually were.
The fact that the very similar quality issues such as fit and finish, manufacturing defects mimic more contemporary models just reaffirms that these new items are not reproductions, unless you found an original Ives locomotive with a sound board.
If you could take apart the internal mechanisms with common household tools and diagnose the problem and fix it then you have a reproduction of the original.