This started failing around R60-9548.0.0. Check links below for details. 

https://wmatrix.googleplex.com/unfiltered?suites=wifi_matfunc&tests=network_WiFi_SimpleConnect.wifi_check1x_WEP&days_back=45&releases=60
https://wmatrix.googleplex.com/unfiltered?suites=wifi_matfunc&tests=network_WiFi_SimpleConnect.wifi_check1x_WPA&days_back=45&releases=60


Sample failure:
05/15 10:25:09.308 INFO |wifi_test_context_:0255| Connecting to SimpleConnect_a_1g1mj_ch1.
05/15 10:25:29.357 DEBUG|      xmlrpc_types:0056| Constructing AssociationResult object with args=[], kwargs={'configuration_time': -1.0, 'association_time': 15.032639026641846, 'discovery_time': 3.3055739402770996, 'success': False, 'failure_reason': 'FAIL(Association timed out)'}
05/15 10:25:29.357 INFO |wifi_test_context_:0263| Finished connection attempt to SimpleConnect_a_1g1mj_ch1 with times: discovery=3.31, association=15.03, configuration=-1.00.
05/15 10:25:29.358 DEBUG|network_WiFi_Simpl:0056| Caught exception during Connect


Traceback (most recent call last):
  File "/usr/local/autotest/client/common_lib/test.py", line 609, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 817, in _call_test_function
    return func(*args, **dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 470, in execute
    dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 347, in _call_run_once_with_retry
    postprocess_profiled_run, args, dargs)
  File "/usr/local/autotest/client/common_lib/test.py", line 380, in _call_run_once
    self.run_once(*args, **dargs)
  File "/usr/local/autotest/server/site_tests/network_WiFi_SimpleConnect/network_WiFi_SimpleConnect.py", line 61, in run_once
    raise e
TestFail: Expected connection to SimpleConnect_a_1g1mj_ch1 to succeed, but it failed with reason: FAIL(Association timed out).

I see few changes in wpa_supplicant. Diff @
https://crosland.corp.google.com/log/9543.0.0..9550.0.0