Pin drift is a fairly common issue. Solutions run from simply replacing the pin to threaded and capped "anti-drift" hammer and trigger pin sets ($$$).
Anti-Walk Hammer & Trigger Pins AR-15 Small Pin .154 Matte Package of 2
AR-15 Antiwalk Trigger Pins
"The whole of the Bill (of Rights) is a declaration of the right of the people at large or considered as individuals.... It establishes some rights of the individual as unalienable and which consequently, no majority has a right to deprive them of." (Albert Gallatin of the New York Historical Society, October 7, 1789)
"A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government." - George Washington