I think I am getting interference but not sure how to track it down.

I have a AP where my customers can download from it fine but the upload is really poor.
The download can get up to 20Mb on 5Ghz N 20Mhz Mimo NV2 but the upload will run 2Mb or as low as 0kb usually the lesser.
Check out this Spectral Scan.
What should I be looking for to narrow down my upload issue.?
Thank you

use 40mhz channal width..and try use another wireless channel with higher ccq.....

I have tried 20/40 Mhz and have tried all channels.

I have a Backhaul that I set at 5900mhz and even it has a poor receive at the tower location.
It seems all the connections that are pointing to the South have poor receive and that is from multiple APs and separate antennas in the 5Ghz range.
I have another tower site that has the same issue and it is pointing in the same direction.

What is the best way to track down interference?

Do you have access to a portable Spectrum Analyzer like the Anritsu 2700 series? I hate to be the bearer of bad news but this will probably require shutting your system down so that you can discriminate the interference from the desired signals. Once you "see" the interfering signals on a spectrum analyzer you will be better prepared to make decisions about frequency assignment. If you find that there is interference there is probably only one mitigation... move. That is the harsh reality of 802.11. I will monitor this thread if you have additional questions.