Duplicates records when register multiple participants

System fails to check registered user for duplicates.
This issue occurs only with contacts that been registered by registrar for some CiviEvent using register for multiple participants . Check for registrar itself works well.
I succeed to produce this bug on joomla demo site here http://joomla.demo.civicrm.org/ using this steps
1) created 3 Individual contacts record from backend
2) submit on-line registration for an Event

• select register 3 participant including myself
• select pay latter option
• for each user entered: First Name, Last Name, Email (same as in step via included simple profile

As result I get 2 duplicates for 2 contacts that have been registered and no duplicate for registar