Original sentence: Lee was scheduled to fly another mission to the International Space Station in 2000, but was replaced by Robert Curbeam for "undisclosed reasons".which news reports claimed related to a falling-out with "at least one of his superiors at the NASA's Johnson Space Center"
Edited sentence: Lee was scheduled to fly another mission to the International Space Station in 2000, but was replaced by Robert Curbeam for "undisclosed reasons" which news reports claimed related to a falling-out with "at least one of his superiors at the NASA's Johnson Space Center"