New iPhone 6 Pluses' finger login problems?

Hello.

My 2/two 60+ years old clients are currently having problems with their new (2/two days) old iPhone 6 Pluses's finger logins. Sometimes their iPhones don't register their thumbs' finger prints to let them in. They have to retry several times or use their passscodes to get in. Is this a known issue?

Both iPhone 6 Pluses have iOS v8.1.3 from Monday (nice timing!). One/1 is a clean state whgile the other one/1 was migrated data from his 13.3" MacBook Pro's Mac OS X v10.8.5's iTunes (all updates). I did notice they, esp(ecially) the female, like to clean their hands and use lotions a lot. I am not sure if that is causing the issue?

Thank you in advance. 🙂