QUOTE(Jjuggler @ Jan 6 2018, 01:50 PM)
I've waited for two minutes before taking the "after" cpu load.
before
[attachmentid=9487754]
after
[attachmentid=9487756]
So, we can rule out transmit power issue, lack of power caused by EHDD and CPU load issue (the load still acceptable).
It is not Group Rekey Interval issue either.....
Double check, does the wifi signal totally gone for all devices when the disconnection happen? Such as the SSID suddenly missing?
You may want consider 5ghz inteference possibility from neighbours

?
Despite manufacturers tend to advertise 5ghz being interference free, most tends to omit the fact their routers only support few 5ghz channels. For C1200, the allocated 5Ghz frequency channels are 36 to 48.
36, 40, 44 and 48 available if 20Mhz is selected.
38 and 46 are for 40Mhz ---> Since you select this, there are effectively two 5ghz channels you can use.
Only 42 is used/available if you select 80Mhz. ---> Only one 5Ghz channel, if your neighbour router is very closeby and he/she also use C1200 and force 80Mhz on 5Ghz....well....the interference.....
EDIT:
If I disable Print Server, stop torrenting, disable OpenVPN, disable folder sharing, disable WPS and little connections.
My CPU usage is:

Perhaps I hit the c1200 silicon lottery?
This post has been edited by JohnLai: Jan 6 2018, 02:14 PM