Facebook Inc. executives have long said that artificial intelligence would address the company’s chronic problems keeping what it deems hate speech and excessive violence as well as underage users off its platforms.

That future is farther away than those executives suggest, according to internal documents reviewed by The Wall Street Journal. Facebook’s AI can’t consistently identify first-person shooting videos, racist rants and even, in one notable episode that puzzled internal researchers for weeks, the difference between cockfighting and car crashes.