The nation’s central bank said that financial system vulnerabilities increased over the last six months, pointing to the blow-up of family office Archegos Capital Management and the run-up in “meme stocks” like Gamestop. “A few recent episodes have highlighted the opacity of risky exposures and the need for greater transparency at hedge funds and other leveraged financial entities that can transmit stress to the financial system,” the Federal Reserve noted in its Financial Stability Report released Thursday.