Just thought I'd share this information for anyone also having trouble
So, I was having trouble re-rooting my S5 after the XXU1ANG2 update for the SM-G900F international model as Odin kept throwing out a FAIL to write error every time I tried. After multiple attempts I finally figured out what was wrong with it. In my settings I'd selected the reactiviation lock, so that If I lost my device nobody would be able to get into it. So unticking this and do the usual root process and voila it works as per!