Brian,
I feel your pain and need to do the same (restore v 10.4 on the iOS devices). I figured out a way to do it through iTunes if this is any help to you - some of these steps maybe overkill, but I wanted to be sure that I was able to grab the correct older version of Collector and install it:
1) Grab an iOS device that has the older version of Collector on it (10.4)
2) On your PC/Mac - delete all older iTunes backups (you can google how to do this)
3) Plug the iOS device with Collector 10.4 into the PC/Mac and open iTunes
4) Find your iOS device in iTunes and select "Manually Backup and Restore" - "Back up Now"
5) After it has finished backing up, disconnect the iOS device from the PC/Mac
6) Grab all of the iOS devices that had installed Collector 10.4.1 on them and remove the Collector application from the device.
7) Plug in each device into the PC/Mac and open iTunes
😎 Find the iOS device in iTunes and select the "Apps"button on the left - find "Collector" and select "Install" - this will install the backup copy from step 4.
9) Select "Done" on the bottom of the iTunes screen, and it will automatically install the older Collector version.
10) Voila - you should now be running a version of Collector that works with Survey123.
I am going to try my best to get on the beta test group for Collector, and I would suggest you do the same. Our business process/function is so heavily reliant on Collector that I live in fear of each version update 'breaking' things - like what just happened with this release. Good luck to you, and I hope that you did not lose too many field hours trying to fix this issue.
mark