Huge drop on Downlink MCS - ePMP2000

Hi guys, I have an issue with one of my ePMP2000, Few days back the Downlink MCS went from 14-15 to 5-6 for all clients on this AP.
I will add as much info from SM and AP here. I’m currently unable to do physical check if antenna got moved but will do that soon. This AP has been running fine for 5 years and from last firmware update also no problems for a year ( 4.6.0.1 ). I did auto channel selection and the quiet part is from 5300 to 5400 but still even after ACS picks the frequency I still have this problem.

Thanks all.

Data:

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Downlink Packets Per MCS
MCS 15 - 64-QAM 5/6
0 (0%)

MCS 14 - 64-QAM 3/4
0 (0%)

MCS 13 - 64-QAM 2/3
0 (0%)

MCS 12 - 16-QAM 3/4
0 (0%)

MCS 11 - 16-QAM 1/2
82 476 (1.2%)

MCS 10 - QPSK 3/4
1 (0%)

MCS 9 - QPSK 1/2
1 556 (0%)

MCS 8 - BPSK 1/2
0 (0%)

MCS 7 - 64-QAM 5/6
3 363 (0%)

MCS 6 - 64-QAM 3/4
2 230 563 (31.4%)

MCS 5 - 64-QAM 2/3
4 307 045 (60.7%)

MCS 4 - 16-QAM 3/4
262 559 (3.7%)

MCS 3 - 16-QAM 1/2
2 071 (0%)

MCS 2 - QPSK 3/4
234 (0%)

MCS 1 - QPSK 1/2
206 464 (2.9%)

MCS 0 - BPSK 1/2
0 (0%)

Uplink Packets Per MCS
MCS 15 - 64-QAM 5/6
48 072 (1.4%)

MCS 14 - 64-QAM 3/4
46 785 (1.4%)

MCS 13 - 64-QAM 2/3
181 695 (5.5%)

MCS 12 - 16-QAM 3/4
2 612 243 (78.4%)

MCS 11 - 16-QAM 1/2
4 247 (0.1%)

MCS 10 - QPSK 3/4
122 (0%)

MCS 9 - QPSK 1/2
237 (0%)

MCS 8 - BPSK 1/2
0 (0%)

MCS 7 - 64-QAM 5/6
289 274 (8.7%)

MCS 6 - 64-QAM 3/4
141 883 (4.3%)

MCS 5 - 64-QAM 2/3
6 841 (0.2%)

MCS 4 - 16-QAM 3/4
138 (0%)

MCS 3 - 16-QAM 1/2
18 (0%)

MCS 2 - QPSK 3/4
50 (0%)

MCS 1 - QPSK 1/2
15 (0%)

MCS 0 - BPSK 1/2
0 (0%)

Operating Frequency 5 350 MHz
Operating Channel Bandwidth 40 MHz
Transmitter Output Power 28 dBm
Antenna Gain 17 dBi
Country Other
Subscriber Module Mode TDD
Network Mode NAT
Downlink RSSI -69 dBm
Downlink SNR 24 dB
Uplink MCS MCS 13 - 64-QAM 2/3
Downlink MCS MCS 5 - 64-QAM 2/3

AP

|Operating Frequency|5350 MHz|
|Operating Channel Bandwidth|40 MHz|
|Transmitter Output Power|25 dBm|
|Antenna Gain|18 dBi|
|Country|Other|
|Access Point Mode|TDD|
|Downlink/Uplink Frame Ratio|Flexible|
|Wireless Security|WPA2|

Power Control
Transmitter Output Power = 25 dBm
Antenna Gain = 18 dBi
Subscriber Module Target Receive Level = -60

Scheduler
Downlink/Uplink Ratio = Flexible
Frame Size = 5 ms
Downlink Max Rate = 15
Guard Interval = Short