I encountered this bug on my druid playing balance spec in torghast (after choosing one of the Anima powers my “S” move button just completely stopped working entirely for the entire run (I shut off all addons, closed game entirely to try and fix it, but it persisted, meaning I assume its caused by an anima power). I was able to type “S” no problem in chat, so it wasn’t my keyboard, and “S” was still keybound to move backwards.
After the Torghast run I exited and my S movement key was working fine once again.