If you’re still interested, ‘Stukkie’ comes from ‘stuk’ which means broken. The -kie that is added is to infantilize the word, usually to refer to a smaller object you’d use -je instead, -kie is more of a dialect which is why you won’t find it in a dictionary. ‘Wukkie’ means as much as the ‘woopsie’ in ‘oopsie woopsie’, to make it sound even more infantile.

So a literal translation would be ‘The train is brokey wokey’