I would suggest the target receive level is fine. Since you have reported one imported clue that the upload is bad. I would suggest to look for RSSI and uplink/downlink MCS for that perticular SM in AP--->Monitor--->Performance page. The upload issue can be due to :-
1.First we should start from configuration part.It could be the downlink/uplink is wrongly set on AP.It might set for 75/25 or flexible.One sided interference.
2.Another issue could be due to one sided interference.
To get rid of interference issue.Run the spectrum analyser at both ends(AP/SM).If you find the channel is available with low noise (about -90dBm or -90dBm +)at AP/SM end.But the same channel has high noise at SM/AP end. Then look for better channel.
Some times the poor alignment was also been reported for poor upload issue.You could look for RSSI of perticular SM. The best tool for this is Tools--->eAlign.To check the RSSI values.
Keep the radio on latest software for any bug fixes,if required.
I would recommend to keep the below point always in mind before start troubleshooting for any PTP/PMP/ePMP throughput or low RSSI or Low modulation issue.These points are applicable everywhere in whole wireless universe :-
Distance/Noise/Alignment/Bad configuration-----could affect--------->Modulation/RSSI-----if low then------>Throughput--------->will be low for sure.
The best way to save all future risk is ------->Plan the link on Capacity Planner for ePMP/PMP, Link Planner for PM/PTP.You will feel the magic after using those tools.
Hope this will help in future during troubleshooting and understanding the co-relations between all above aspects.