Prepared the locomotive, turned on the alerter(shift + num enter). Ran up to the cars, coupled them. And that's it. From the moment of coupling, the locomotive does not react to throttle lever. Just dead. Turned off the alerter(shift + num enter) and - a miracle - the locomotive came to life! I was in the cabin the whole time and the alerter didn't make a sound!
Yes, I noticed this happening, I just don't remember the route this happened on. The wonders of TSW never stop giving.