I tried searching but couldn't seem to find anyone else struggling with this. When attempting to complete this cairn, I have gotten a tower that seems stable and meets the height requirement only for the wedge stone to begin vibrating violently causing the whole tower to fall. I have replicated the issue and even clipped it on the PS 4 but it is rendering this mystery impossible to complete.
Hello there @MaeBell_16! Welcome to the forums 
I'm sorry to hear that you've had trouble completing the cairn in Hamtunscire. I have vivid memories of completing this one myself, and it definitely took a lot of time 
You've mentioned that you've been able to capture a clip of the vibrating wedge stone. Would you be able to share this video with us within this thread? I'd recommend uploading the video to YouTube directly from your console, as this will allow you to post a shareable link within this thread for us to take a closer look at. Being able to see how this issue is reproduced will be helpful for further investigation.
Thanks! 
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