1. Are the APs joined on the same WLCs?
2. Is FT enable?
3. Is that specific AP on flexconnect and in standalone mode or has lost association with WLC?
4. Are the APs on different AP Groups and/or Flexconnect Groups?
5. Is WPA gtk-randomize State enabled?
6. Can you please show the output of "show advance eap"
did you find the solution at this problem?
I'm having your identical problem and I have also opened a TAC but I'm still without a valid solutions.
I can add that the problem is present also with FT disabled.
Check if you are using FT if yes disable it and try again. If no check if you are using K,V deactivate it and test it. Check the debugs and see if client and AP are responding correct during epol key exchanging. It did not help us to tune epol timers.