I don't think this parser parses left-to-right, like humans and other parsers like Parsley MacParseface do.
Their results for even the most simple english sentences are horrible, often with multiple mistagged words.
As soon as you add relative clauses, they break down entirely.
I've used the Stanford parser for university work (at Masters level). It was part of the pipeline for a sentiment extractor. I didn't get the feeling it performed badly, quite the contrary- the parses it generated were quite useful as features in my extractor. It had this rare feeling of a tool that you can actually use to do something interesting and useful.
Then again, I do have my expectations set very lowly, for this sort of thing, especially after completing my Masters thesis (on grammar induction). Language learning is hard.
Any every slightly more complicated sentence was completely misparsed by CoreNLP and ParseyMcParseface. As I mentioned before, as soon as you introduce relative clauses it breaks down.
It's hard when your research was supposed to discuss how to better handle the common knowledge problem of NLIDBs, but you have to spend a lot of time just to get a kinda useful parse out in the first place.