so if you set any e500 AP to channel 2 (2417MHz for 802.11b or 20MHz channel bandwidth 802.11g/n/ac mode) you get a large increase in the noise floor around 2417MHz at the other e500 access points is that correct?
pic1 and pic2 seems to show a higher noise floor, but 3-5 do not. Have you adjusted the TX power setting for the channel 2 Transmitter? The TX gain setting does have some tolerance (+/- 2dB) and Channel 2 might be on the high-side of that tolerance in some cases. Also, the antenna pattern might be a bit better for that particular channel vs. other channels and give a bit more gain.