Due to the massive size of itself, The ISS has to do many orbit reboost during times, which is far more often than other amsats and current sources often caused inaccuracy, so i'd suggest to use the official source of TLE
https://live.ariss.org/tle/ for the ISS, where you can get the raw and clean TLE text from
https://live.ariss.org/iss.txt.
Alan.