I am having some strange issues with an EAP225-Outdoor as a single AP in stand alone mode.  It only happens on the 2.4 Ghz band, not the 5 Ghz band.  Here are some of the issues:

• Slow for clients to connect, more pronounced with mobile phones than with computers.
• Portal page will not load, device sits at white screen until a timout occurs.  Only affects mobile devices and only on the 2.4 Ghz band.  Portal page has since been disabled.
• Sometimes devices will not connect at all, again more pronounced with mobile devices.
• Sometimes after being connected, an IP address is not issued and the client device shows "no internet connection".  Connecting to the 5 Ghz band resolves this immediately.
• Once connected, device response times while doing normal activities is poor.  Speed test and ping are generally fine, but web browsing, email, text message updates sometimes struggle.
• Overall, I find the 2.4Ghz band relatively unstable, sluggish and not very usable.  5Ghz band works perfectly in all situations.
• If I reboot the EAP225-Outdoor, then the 2.4 Ghz band snaps back into shape but after some usage/client load the issues resurface.

The EAP225-Outdoor is set to Channel 11, 20Mhz bandwidth.  SSID's are separate for 2.4 and 5.0 Ghz bands.  Installation environment is a marina with one other primary SSID (AIM - owned by the Marina) utilizing Open Mesh hardware operating on Channel 1 at 20 Mhz.  In general 10-15 clients connected at any given time, with most connecting to the 5.0 Ghz band as that is more reliable.  I have also reset the EAP225-Outdoor to factory defaults and reconfigured, that seemed to help but did not resolve my issues. All advanced features of load balancing, airtime fariness, and band steering are disabled.  

As mentioned above I have separate SSID's for the 2.4 and 5.0 Ghz band.  I did try a single SSID for both, however with the issues on the 2.4 Ghz band that was not an option since you cannot force use of the 5.0Ghz band.  And despite the increased performance and range of the 5.0 Ghz band, most devices choose the 2.4 Ghz band by default.

As a side note, I did a test with a Ubiquity UAP-AC-M-PRO and with the exact same settings the 2.4 Ghz band worked perfectly, however the 5.0 Ghz performance was terrible (Signal -22DBm for 5.0 versus 2.4 due to antenna radiation pattern).  So this proved that 2.4 works and may not be an interference issue, but again I am not able to rule that out.

I have done a site survey (2.4 Ghz band results attached), and SNR and overlapping channels/SSID's appears ok.  There are 4 other SSID's on Channel 11 but all -80 to -90 DBm versus -50 to -70 for the EAP so I don't think I have an interference issue but that is certainly possible.  I also see there is a firmware update for the EAP, so I need to apply that as well, however I don't see much in the relase notes that addresses the issues I am seeing.

Any thoughts or help would be appreciated.