IOS: chSystemInfo.deviceUniqueIdentifieranges when app UPDATE

We have a very unpleasant problem on IOS: SystemInfo.deviceUniqueIdentifier changes when we publish new version (forcing app to update).

About 2-5% of users fails to login after update becouse they has new SystemInfo.deviceUniqueIdentifier !

This is extrat update of app, not reinstall.

I don't know how to fix that problem. We can't update app our app due mass login problems!

How to fix this ? Or what to use insted SystemInfo.deviceUniqueIdentifier ?