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!
Just thought I'd share this information for anyone also having trouble