I believe this is working properly. By that, I mean when you try to put the "Unending Loyalty" buff on someone who already has it, it can't give them that buff.
I believe this is a consequence of the the buff not being able to be dispelled. As a result, it tries to place a new buff, but can't replace the old one.
I believe the same thing happens with Padme's Protection up when it can't be dispelled. It's possible they are both broken, but I think it's at least consistent among buffs.
Now, I will note that this doesn't seem to affect debuffs. For instance, JTRey does not seem to have a problem reapplying (and getting a new duration) on her Healing Immunity debuff.
