I have an application that uses CoreData as a persistent storage and recently implemented the support for iCloud-Sync. All works fine with my test devices (iPhones) and for most my users the synchronisation works as intended.
However I have been getting a few emails lately, notifying me that the iCloud synchronisation does not seem to work for some users. All of those users are using iPhone devices and are trying to sync the data of the app to an iPad (or the other way around). It also only seems to be working one-sided. Data which is created on the users iPad syncs to their iPhones fine, however the iPhones data does not sync to their iPad.
I think this is a weird issue and I haven't been able to resolve it yet. My app is designed for iPhone (iOS) only so far, so the iPad users are using the iPhone version on their iPad.
What could cause this issue and how can it be resolved? Would be really grateful for some guidance!