Following but not attacking?
Sounds to me like what happens to me some times. I walk into a spawn(any) and a creature or two instead of targeting me just starts to follow at mounted speed.
My 1st super dragon taming attempt went like this. I brought in a cu tanked it down to redline then recalled away to stable it. When I came back I had a dragon and a wyvrn in follow mode. As if I asked them to do so!. They started following me from across the whole of destard! They didnt attack me until the beast was tamed. Then wham they both engage me at the same time. I attacked them with the newly tamed and mostly dead super dragon and lived miraculously! That super dragon now resides in my stables as a reminder of how screwy thing are some times!
Its a bug.
Also I had this happen to me while soloing the darkfather with my bard. A stray rotten corps up and decided to follow me. Not attack, but just follow me. Once I engaged him it stopped but he was moving as fast as a mounted player and i couldn't shake him at all. Scary!
Some times the code for this following phenomenon fixes its self in a few minutes some times not. Its a mild inconvenience at best but it does happen to me a few times a week.