Sadly this is not a new issue, it is one I have and have also reported on the forum. I main WHM but it got so bad I considered a new job but before I threw the towel in I got my hubby to film my screen and my KB as I couldnt consistanly reproduce the glith I thought we will catch it on film and also my fingers to make sure it wasnt something I was doing!
As a result I was able to see that when my cures were hitting me and not my target it was because I had my back to them and the "auto face your target" function had failed to kick in! Thankfully that has resolved 99% of these failed cures as I can make sure I manualy turn towards my target before casting, and if I dont I can now catch the failed cure before wasting any mp! hope this helps everyone else having this issue too!!