ACR X TCASII RA CLB HAD LTSS FROM CPR Y. EVASIVE ACTION TAKEN. SYS ERROR.

Narrative

ACR X WAS DSNDED AS PER NORMAL OPERATING PROC. AFTER SEEING POTENTIAL TFC; I TRIED TO RESOLVE BY RECLRING ACR X TO ANOTHER ALT; BUT MISTAKENLY STATED WRONG ALT. ACFT PASSED WITH 2.3 MI LATERAL AND 600 FT VERT. SUPPLEMENTAL INFO FROM ACN 202172: ACR X WAS INADVERTENTLY DSNDED TO FL240 FROM FL270 BY RADAR CTLR. I WAS ASSISTING CTLR WITH MANUAL DUTIES WHEN I NOTICED ACR X WAS GETTING CLOSE TO LOSS OF SEPARATION WITH CPR Y. BASICALLY SEPARATION WAS LOST (600 FT/2.3 NM). THIS WAS ATTAINED AFTER ACR X WAS ISSUED A CLB BY THE CTLR AND HAD SIMULTANEOUSLY CLBED DUE TO A TCASII ADVISORY. THE TCASII ADVISED ACR X TO 'CLB' WHEN THE CPR Y WAS AT FL262 DSNDING TO FL250 AND WAS APPROX 10 NM FROM CPR Y. CPR Y WAS ISSUED DSCNT; BUT IN KEEPING WITH HIS PREVIOUS FREQ PRESENCE AND SLUGGISH RESPONSE; HE NEVER TOOK THE CLRNC. THE THING TO BE NOTICED WAS THAT TCASII DID; IN FACT; AID IN THE PHYSICAL SEPARATION OF THE 2 ACFT. HOWEVER; I BELIEVE THAT THE TCASII CHOSE THE WRONG SOLUTION AND SHOULD'VE 'DSNDED' ACR X FROM FL262 TO FL250 AS PER ATC INSTRUCTIONS AND THIS WOULD'VE PROVIDED A MORE EFFECTIVE MEANS OF ACFT SEPARATION. SURELY; IF THE CTLR WOULD'VE NOTICED THE INCIDENT. WHILE ACR X WERE STILL DSNDING AT FL262 AND 10 NM FROM CPR Y; HE WOULD'VE HAD ENOUGH TIME TO PREVENT AN ERROR.