ACR Y DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM CPR X. SYS ERROR.

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CPR X WAS SWBOUND OVER L0Z; KY. CPR X DSCNT WAS ISSUED TO FL330 IN ACCORDANCE WITH ZID/ZTL LOA. A HDOF FROM ZTL WAS RECEIVED 5 NM NW OF TYS AT FL350. I WAS WORKING THE SME (SOMERSET SUPER HIGH) RADAR SECTOR. MY D-SIDE (MANUAL CTLR) UNDERTOOK TO COORDINATE WITH ZTL TO HAVE ALL ORD INBOUNDS DSNDED TO FL310 OR BELOW. ACR Y WAS OVER TYS AT FL350 ENRTE TO ORD. MY D-SIDE WAS COORDINATING THE DSCNT ON XYZ235 WHEN I BROUGHT HIS ATTN CPR X AT FL330. I OVERHEARD HIM SAY 'LEAVE HIM AT FL350 RBL HAS THE HDOF; THEY'LL WORK HIM DOWN.' MORE WAS SAID I DID NOT HEAR. I SAID 'THEY'RE LEAVING HIM AT FL350' AND WAS TOLD 'HOLD ON; I'M COORDINATING.' WHEN MY D-SIDE GOT OFF THE LINE I ASKED WHAT WAS BEING DONE. I WAS TOLD 'ATLANTA IS SEPARATING.' I ASSUMED THAT MEANT ACR Y WOULD REMAIN AT FL350 AND GO OVER CPR X AT FL330. I THEN OBSERVED A MODE C UPDATE OF FL342 ON ACR Y UNDER ZTL CTL. TURNS AND DSCNT WERE ISSUED TO CPR X IN AN ATTEMPT TO PROVIDE SEPARATION. ACR Y RATE OF DSCNT WAS IN EXCESS OF 3000 FPM; PLACING HIM BELOW CPR X IN 2 UPDATES OF RADAR; ROUGHLY 1 MIN. CPR X WAS RECLRED TO FL330 AND RESUMED OWN NAV TO MEI. SEPARATION WAS LOST (FRACTIONALLY LESS THAN 5 NM) AND REESTABLISHED IN 30 SECONDS. SUPPLEMENTAL INFO FROM ACN 219191: I HAD COORDINATED WITH ZTL THAT THEY WERE PROVIDING SEPARATION ON ACR Y AND CPR X. ZTL DSNDED ACR Y TO FL310 FROM FL350. CPR X WAS AT FL330. I TOLD RADAR CTLR THAT ZTL WAS PROVIDING. AS ACFT GOT CLOSER; RADAR CTLR DSNDED CPR X TO FL310 INTO CONFLICTION WITH ACR Y. RADAR CTLR BELIEVED ACR Y WAS STAYING AT FL350.