I'll pick up the thread. The SEC has initiated an investigation into Circle.  The company first reported interest from the regulator in August, but the information went unnoticed.
According to the new S-4 Form, in July 2021 Circle received a summons demanding to provide documents and information regarding certain assets, client programs and operations. https://www.sec.gov/Archives/edgar/data/1876042/000110465921122565/tm2124445-1_s4a.htm