Hi, I looked at this today and found a workaround. See the attached XLSFile. I created Groups to consolidate the relevant expressions that were not working. This had a double effect:
1) The relevant expression executed correctly.
2) The Survey loading time was reduced (because fewer expressions needed to be evaluated).
The above may help but still does not explain why this works in Android, Windows, Mac but not in iOS. Typically when I have seen this happening before it was due to case-sensitive issues (iOS is case sensitive for some things that the rest of operating systems are not). We will need to look into this a bit more closely, but I hope the workaround above works for you.