Can you Export from the A360 dashboard of the design (please export an Archive *.F3Z file)?
Next, can you create a public link of this F3Z file and share it with me Nathan.Chandler@autodesk.com?
This file will help me to better understand the root cause of the error.
One suggestion may be to re-open the updated assembly and perform a Compute All from the Modify drop down menu. If there are any errors or warnings in the timeline, resolve them and then save a new version. Last, re-open this design and attempt to update again.
Hope this helps! Let me know if you have any questions.
Nathan Chandler
Principal Specialist