Rails are stretched at time of installation in accordance with a temperature formula. Some times they heat the rail if air temps are too cool. Still have to use rail anchors to assist in stability. But, sometimes in spite of all the precautions they still will get a kink. Likewise in extreme cold snaps rail will actually pull apart due to contraction. In places where there are long down grades rail will actually creep down hill and sections will have to be cut out or kinks will occur from that too. That may or may not have had an effect on the D&S rail.
There has been a lot of discussion by professional railroad men on Trainorders.com about kinks.