Hi Michael
Thank you for this quick answer.
I have to double check, but as far as I remember, both IAP started on channels above 100...
Still I'ml wondering why the two IAP behave differently (AP #5 works as expected, i.e. 5GHz up 60s after 2,4GHz)...
Nevermind, I will do some additionnal tests and post the results in this thread and then I shall mark it as closed if the long delay is confirmed (4-5mn are still acceptable in a site survey context).
Have a nice day.