I saw the 464 at Huckleberry while it was being rebuilt. At the time the boiler had just been placed back on the frame and had its lagging but not its jacketing. The running gear was in pieces. The tender had been rebuilt but not painted.
Not to knock the guys at Knotts, because the D&RGW was probably the real culprit, but the shops guys at Huckleberry said the locomotive was really a hulk when they got it. The frame was in really bad shape. They had to make new axle boxes and the running gear had been operated without repairs for so long that entire pieces would have to be made from scracth. They showed me some pieces that were kind of a funny oval shape that was sort of a square oval. They said these pieces were supposed to be completely square.
They did a masterful job of rebuilding the 464. I forgot. When I was there they had just finished the new wood cab and had just painted it for the D&RGW scheme it had when it finished operating at Durango.
I have had a chance to ride behind the 464 since her initial rebuild and the Huckleberry shop crew did a masterful job with it.
My guess is Knotts just did not need to put the time and money into what was a completely worn out hulk.