Sounds like a combination of things...a locomotive working at near its capacity going upgrade, pushing its way through unplowed snow, and ice-plugged sand pipes (according to the video poster)
According to the description (and a quick trip to Wikipedia), the originating city, Varaždin (Croatia) is at about 500 or so feet elevation. Zagreb, the next stop could be anywhere from 400' to almost 3400'. so it could very well be a steep grade taxing the locomotive.
---PCJ