ZSE CTLR PROVIDING CTLR INSTRUCTION IS UNABLE TO ESTABLISH SEPARATION DUE TO DEVELOPMENTAL ERRONEOUS CTL INSTRUCTIONS.

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I WAS WATCHING MY STUDENT AIR TFC CTLR ON SECTOR 6 IN ZSE'S AIRSPACE. TFC WAS MODERATE WITH ROUTINE COMPLEXITY. ACR Y WAS NBOUND AT 16000 FT MSL ON AN IFR FLT PLAN FROM MFR TO SEA VIA DIRECT OLM; OLM2 ARR. ACR X WAS ON AN IFR FLT PLAN FROM PDX TO OAK VIA DIRECT EUG; CLBING TO 15000 FT MSL. MY STUDENT TOOK THE HDOF FROM PDX APCH AND CLBED ACR X TO FL230. FOR SOME UNKNOWN REASON I MISSED THE CHK-ON AND CLRNC FOR ACR X. THE CONFLICT ALERT FUNCTION SOON WENT OFF AND I ASKED MY STUDENT IF WE WERE TALKING TO ACR X. HE RESPONDED BY SAYING 'NEGATIVE.' HE THEN RECLRED ACR X TO MAINTAIN 15000 FT. ACR X RESPONDED WITH A COMMENT STATING HE WAS DSNDING BACK TO 15000 FT. MY STUDENT THEN TURNED ACR Y 50 DEGS L AND RECEIVED NO RESPONSE. I KEYED UP THE MIKE AND ISSUED ACR X A L TURN TO 130 DEG HDG. SOMEONE RESPONDED WITH 'BLOCKED.' I REISSUED THE L TURN TO ACR X. SOMEONE RESPONDED WITH 'BLOCKED;' AGAIN. AT THAT TIME THE PLT OF ACR Y STATED HE WAS RESPONDING TO A TCASII RA BY DSNDING. ACR X THEN RESPONDED WITH A TCASII RA BY CLBING AGAIN. SEPARATION WAS LOST AS THE TARGETS MERGED. I SHOULD HAVE CAUGHT MY STUDENT'S CLRNC TO ACR X. I WAS PAYING CLOSE ATTN; BUT STILL MISSED IT. IF WE LEFT THE ACR X CLBING TO FL230; CHANCES ARE THE ACFT WOULD NOT HAVE GOTTEN AS CLOSE.