Kaddressbook with etesync always create duplicate entries

Hi, I’ve used etesync to sync contacts on android,ios and kde. I have tried several times but it seems kaddressbook always produce duplicate contacts for almost every contact entry. Funny how when I use ‘tools-search duplicate’, it reports ‘no duplicates found’ even although I see dozens of duplicated entries (same name same content).
On android or ios it shows the correct contact entries from the etesync account.

What’s worse is that if I delete the duplicated entries, it would delete some entries in my etesync account too which would cause some missing entries on other devices but only exist in Kaddressbook.