The value "Error Drop Packets" is so big.

Dear everyone,

The distance between AP and SM is about 0.5m, total is ideal but I have not got the best value, the value "Error Drop Packets" is so big, as attached file.

Can you help me ?

I would look for interference at the client end - like a wifi router near the SM running on an overlapping channel, or multiple APs on that channel all visible to the SM. (sync and identical settings should alleviate, but distinct channels is the only certain fix) What do the units report as the SNR uplink and downlink, and the MCS?  (If interference, you'll likely see the downlink SNR pretty low)

Only certain proof would probably be running SpecAnal on the SM, which you can't do remote.  But if you can change the AP channel without causing catastrophe you can try a couple other channels and see if you note improvement.