Q: iPhone 6s having problems syncing. Stops at Contacts. iPhone 6s  was upgraded from iPhone 5.

Hello, adamapple8.

Thank you for visiting Apple Support Communities.  

I understand you are experiencing an issue with contacts syncing via iTunes.  Here is the troubleshooting guide that may help resolve this issue. 

If you can‘t sync contacts and calendars using iTunes for Windows

I would also recommend looking into syncing contacts and calendars over-the-air via our free iCloud option.  

iCloud: What is iCloud?

Cheers