ahhhh Glad I came across this post and it is dated for the year....
I was maxed on all my companions on my republic vanguard. I am now zero on all affection. Playing through the Hutt Cartell story lines I noticed it. Frustrated, as last weeks patch didn't resolve it, but also, have a GREAT deal of time vested into this particular (like playing the republic vanguard ala Capt. America ) Granted I have characters on all sides, and areas, none maxed saved this one.
I noticed none of my other characters seemed to have suffered from this, just my highest level one? See I am not alone in the issue, just wondering what the resolution is? I suppose the solution is to play other characters now instead of my highest and keep hoping (?) the next patch will fix it?
Ended up stripping everyone down to see if something may have been bugged by equipment or weaponry.