B737-800
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 14
Communication Breakdown; Situational Awareness; Workload
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Undershoot; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Company Policy; Environment - Non Weather Related; Human Factors; Staffing
Worked Assist side for 30 minutes and then was moved to another sector and worked that position for about 30 minutes. Then I was moved to another Radar position for about 10 minutes; then was told to go to another sector to get the controller out and combine two sectors. The Controller in Charge (CIC) at the time believed he was doing the right thing because people were approaching 2 hours on position. I told him not to combine it but he did it anyway. I had many aircraft on my frequency with many requests for deviations for weather and altitude changes. I had Aircraft X at 29000 feet I told him to cross BETIR at 20000 feet. I saw conflicting traffic at 27000 feet who was a factor for Aircraft X. They were about 30 miles apart and converging. I told Aircraft X to descend to 26000 feet at 2500 feet per minute or greater and then I called the traffic to both aircraft. In the meantime I was super busy scanning and trying to do other things at the same time. The aircraft descended at a good rate but he stayed at 26000 feet over BETIR. I made multiple calls and the aircraft could not hear me due to horrible frequency coverage here at San Juan. The CIC was able to get a hold of Santa Domingo Center and coordinate the aircraft again.
A ZSU Center Controller reported they were forced to combine sectors against their wishes. The Controller assigned a climb rate to an aircraft but the aircraft did not comply with the instruction.