MBP / MBA Failing to reconnect to WiFi after sleep

Hi Guys,

I know this has been covered a hundred times but I am still unable to find a working solution.

I have two machines, a Macbook Pro Retina 15" and a Macbook Air 13" (Mid 2013) both running 10.10.5

(This doesn't happen all the time, maybe 1 out of 10.) Upon waking from sleep, the machines will attempt to reconnect to the WiFi network, it is lighting up the bars as it searches for the network. When you select the dropdown list, the correct network is selected. It will eventually timeout and present an "!" over the WiFi symbol. Looking at the settings, it gets a self-assigned IP address. The only resolution to this is to turn the WiFi off and on again, which then connects immediately.

The WiFi system is running of a ZyXEL NXC2500 with five access points. One stationed in every room of the office.

The main network, "WLAN NETWORK" is broadcasting on 2 and 5 GHz.

The second network, let's say, "WLAN NETWORK 2 ONLY" is broadcasting on 2 GHz only.

This issue occurs regardless of what network the laptops are connected to.

Here are the steps I have already tried:

Disabled Power Nap

Reset the SMC

Reset PRAM

Unchecked, "Wake for WiFi Access" (Both battery and when plugged in)

Unchecked, "Put hard disks to sleep when possible" (Both battery and when plugged in)

Set IPv6 to Link Only

Deleted keychain association with current WiFi network.

Removed WiFi from list and added it.

Moved WiFi to top of the preferred network list.

Deleted Bluetooth .plist file

Deleted SystemConfiguration .plist folder

The only change I have made today is that I realized our WiFi network was set with the CH country code where as we are located in Germany.

I know the macs can get "confused" if there is a country code conflict but CH and DE have the same available/non available channels regardless.

I was starting to think this was an issue with the WiFi controller but our environment is mixed and this never occurs on any of the Windows machines.

I have already ordered two of the "EDIMAX EW-7811UN Wireless Adapter" dongles to see if that would solve the issue but that is a band aid rather than a solution.

I have attached a log file from one of the machines. The issue occurred around 11:27. (Note, that not all above steps were taken above before this log was produced.) Since it seems to be only occuring with two of the "C" level employees, it is quite difficult to get their laptops the moment it happens to investigate. See here: http://solatechsolutions.com/wp-content/uploads/2015/09/Log1.txt

Anybody else have an idea?