Experiencing the same issue with the unpacking error.
We Used Survey123 Connect to set up the survey and has worked well from web browser to app. Tested on our side and had no issues. We presented this to our client and everything checked out. Our clients were ready to put it in use when this error occurred. They are using the Survey123 app and are using AGOL credentials since this project is meant for organizational purposes only.
I'm awaiting reply on what kind of device is having this issue but I'm curious if there is a clear way to get around this problem. I've tried and suggested possible solutions here and the reported Bug on the matter.
Thanks
JTedrick-esristaff