Listening to a Finnish children learn English there are some cases where they struggle and perhaps some of it is vocabulary, "fall" vs "fell", "freeze" vs "froze" (i.e. past tenses).

But there are lot more gotchas and I think pronounciation is one of the biggest gotchas. Finnish is a bad starting point as the language has very regular pronounciation, but hearing a child read new text it's obvious how difficent pronounciation is to learn for even everyday, commonly-used words.