I just failed a tale (a Reda contract if that matters) and after I left the menu where I could pick the fight a clone of Riekr (from one of the two secret stories, don't know which) was still there and shooting arrows at me for a couple seconds but disappeared before I reached the arena floor to fight her.
@xbl_laberbacke Hey there, sorry to hear you ran into this issue and apologies for the late response.
Did this just happen the one time? If it's still occurring, can you record a video?
Also, do you know if you used any boasts during that trial?
Hi @xbl_laberbacke apologies for the late response.
If you happen to experience this issue again could you please record a video.
I would recommend uploading your video to a video sharing platform such as YouTube, you can then copy the URL link into this thread.
Thanks for sharing your experiences and feedback regarding Kara's Arena, @XBL_Laberbacke & @SpirantCrayon22. I'm sorry to hear that you encountered some issues, and we've forwarded this feedback to the dedicated teams. Thank you for taking the time to share how you were able to make your Arena encounters easier, @SpirantCrayon22. Hopefully your tactics can help others who may find these battles tricky.
If you encounter any trouble whilst in Kara's Arena, please don't hesitate to reach out so we can look into this further. If you have any additional feedback you'd like to share, please feel welcome to post it within this thread as well.
Thanks! 
devtrackers.gg