He is a stick-face.
“He is a stick-face” is a literal translation that doesn’t make any sense in English. Based on my research, “He is hard-nosed” is the closest I can think of, or maybe “stone faced,” but that doesn’t capture the idea of stubbornness that the original seems to imply.
Interestingly, the corresponding Tatoeba sentence is linked to “He’s such a shameless jerk.”
@seveer, may I ask where you found this sentence? It doesn’t seem to be in any “legacy” collection.
Well then call me stick-face! 
I’m just going by a few posts by natives that I found on a language forum. Doesn’t seem like it is necessarily quite that harsh, but I could be wrong.
Maybe it has different meanings in different areas. The Tatoeba sentence is marked “Spanish from Chile”.
@morbrorper Well, this is embarrassing. It was apparently from one of my custom collections so I have no one but myself to blame! I had no idea you could create discussion posts from custom collections (even private ones?). Unfortunately I don’t see any way to view the source collection when you are in Review All mode and you can’t globally search your custom collections, so it’s kind of a pain. Oh well, I’ll leave it up in case someone finds this useful.
No problem! I actually don’t see that as a bug.
I agree. There are many paper-cut issues with Clozemaster.