ZOB CTLR; PROVIDING RECERTIFICATION INSTRUCTION; DOES NOT ENSURE VERT SEPARATION BTWN CLBING DSNDING TFC.

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I WAS PROVIDING OJT (MONITORING) OF AN FPL CTLR THAT HAD BEEN ASSIGNED TMU DUTIES AND HAD RUN OUT OF CURRENCY. MFD SECTOR WAS VERY BUSY AND COMPLEX AT THE TIME WITH 14 ACFT (MAP FOR THIS SECTOR IS 12). ACFT Y WAS A PIT DEP STUCK AT FL200; E OF MFD; AND A 'FLY IN THE OINTMENT.' ACFT Y WAS 10 NM INSIDE SECTOR BOUNDARY AND RADAR CTLR HAD TO CALL ZID; CMH SECTOR; ISSUE A 20 DEG L TURN TO AVOID ACFT X. ACFT Y CHKED ON FREQ AT FL230 AND WAS ISSUED CLB TO FL250. BEFORE THE 20 DEG L TURN BECAME APPARENT; THE RADAR CTLR ISSUED A 30 DEG R TURN TO AVOID ACFT Z SWBOUND J83 AT FL220. ACFT Z WAS DSNDED TO FL210; AND I AGAIN OVERRODE THE FREQ AND ISSUED FL210 AND TOLD PLT TO EXPEDITE. I THEN INSTRUCTED RADAR CTLR I WAS MONITORING TO ISSUE TURNS. ACFT Z PLT STATED THEY DSNDED TO FL210 CONTRARY TO TCASII RA. ACFT Y WHO WAS AT FL220 AND SUPPOSEDLY EXPEDITING TO FL250; APPEARED TO DSND FROM FL220 TO FL210 (POSSIBLY AND RA); WHICH ACFT Z PLT CONFIRMED. THIS CAUSED THE ACFT TO GET MUCH CLOSER THAN THEY WOULD HAVE HAD THEY BOTH FOLLOWED ATC INSTRUCTIONS. ACFT Z ADVISED THAT THEY WILL FILE AN NMAC RPT. SUPPLEMENTAL INFO FROM ACN 519614: NBOUND CLBER TFC ENRTE. NBOUND TFC TURNED 30 DEGS R FOR CLB UP TO FL250. TURN INSUFFICIENT SBOUND ENRTE AT FL210. 14 ACFT IN SECTOR (COMPLEX). POOR JUDGEMENT WAS USED IN NOT STOPPING NBOUND CLBER BELOW TFC. ALSO; NBOUND CLBER APPARENTLY DSNDED IN RESPONSE TO RA.