On my Q on the latest 10.2.0.1767 I have duplicate contacts (i restored my earilier) I have 1567 contacts which are now sitting around 1800+ cuz of duplication...
There are a lot of apps that merge duplicate contacts. Try contact x or if you're using Gmail or outlook, their Web services offer this. Also, why restore contacts from backup when cloud services are more effective and efficient at producing contacts database on your phone?
Tapped out on Halle (Black)Berry aka Z10 running 10.2.0.1443
One workaround for duplicates is to shut down phone, pull battery AND sim card momentarily and replace sim and battery. Phone restarts and some dupes are gone (sim card duplicates)
Go into account settings and delete local contacts
Via CB10 from Scotland while pretty stoned using Z10STL100-2/10.2.0.1767
This, and if you have more than one email on the phone, see if contacts are being saved to both accounts. That's what I had happening, as well as locally on the SIM card. It took about an hour but I went through and deleted all contact info on everything but the one primary email account, and then turned "off" the contacts on the other emails & SIM card. That solved the problem. Then on this most recent leak, when adding the accounts I only imported contacts from the one account, so the other accounts don't even give an option to show contacts. No problems since. It's a slight PITA to go through and verify the contacts on the other accounts are listed in your primary, but once that's done it's smooth sailing from then on.
On Z10 - Have around 19000 contacts on ALL contacts. Tried various apps from BB and Sideloaded. These increased from 13000 to 19000. Sure its consuming a lot of space in the memory. Also, if I search for a contact it takes ages, cos surely the device has to search through the thousands of contacts. Please help. Its agonising.