@ArcherC8 Hi thx for replying...

I am.in touch with TP Support ..

To answer your questions/suggestions..

I tried almost everything.. I did not touch my router it started all.of a sudden.. I tried factory reset, unplug the power for some time, different lan ports, switching between channels,  .. nothing worked .. I have only one lan cable and one wan ... no massive downloads .. nothing ... 

If I plug my desktop directly and the router is not on the circuit everything seems to be ok with the router and of course the internet is fine (ping tested) ...

however when the connection goes throigh the router it keeps on restarting every few minutes (leds will go off, then the power led starts blinking like while during booting, the the blinking if power led is faster and next all go up and the internet is working for a few minutes until the next reboot ..  and all over again)

I tried everyrthing I did before when I had issues with other routers or what I was able to google about this issue and router ... nothing helped .. I am kinda desparate.. I don't even now what could trigger this situation ever since I configured the router (a month and a half ago) it was working grear and now this ...

:(

@Mr.p 

I sort of guessing here, but the problem might be on the PC? Even though it works fine connected to the Modem, it might be the problem. If you leave the cable from the PC connected to the router and disconnect the cable from the PC does it still reboot? If not that would sort of indicate it was the PC? Do you have another LAN device you can connect? A different cable even?

@IrvSp 

hmm weird but interesting ... I would never think it could be the server pc (desktop-linux) 

I gave it a try and connected to the router via wifi instead of cable and boom... seems to be stable... might be bec the router was off for a while (was using my old backup router asus) or bec of this ... either way, it's a good starting point ... the resposne time now (via wifi) is slower on that server machine (20ms-> 40ms) but still ok.. I will try to play around with a diff cable or evetually check wireshark to know what packets are being sent to the router (my server is running on Ubuntu) 

thx I gotta run to the office now but will keep u posted later.. I am very curious what is going on there..  so far it seems stable (appprx 20mins without a reboot)

btw I quickly check the logs on the router and the error is still there... tho no rebooting :)

@Mr.p  Try a different power adapter.  Match the voltage (usually 12v) and (ideally) a current rating same or higher as the original adapter.  For testing purposes you can usually undershoot by 0.3 to 0.5A.  

If that doesn’t help then the main router board electrolytic capacitors may be dried out (can be replaced by experienced person) or the silicon may be cooked (flash memory chip and/or radio chips usually seem to fail first in my experience).   Most of these failures  are caused by years of excessive heat, although the flash chips fail eventually regardless , as they have a limited number of lifetime re-writes. 

If it’s toast, attach a small USB powered fan to the next unit, running 24/7.  You’ll get ten years..

Mr.p wrote

btw I quickly check the logs on the router and the error is still there... tho no rebooting :)

For what it's worth, my C9 started doing this in the past week or so as well. Mine seems to have 'reboot episodes' 3 or 4x per day where it will reboot several times in a row in short order. I too saw all of the 'config importing failed' errors in the logs. I read about the NTP config but verified I'm using good/valid US-based NTP servers.

After looking at the logs a bit more this morning, I realized that there was another part to that 'config import' message. Specifically, it mentioned something about "Led". I then saw that in the Router Settings, under Advanced -> System Tools -> there is a setting called "LED Control". In that control, you can toggle "LED Status" on/off. I've set the status to off and have now gone ~6 hours without a reboot or any of the error messages in the system logs.

I will post back with an update.

@nwnomad 

Seem to have the exact same issue as you. 

Any update on how to get it right? Did it work by turning off the "LED Status"?

@Zimpa I don't know how to explain that...but here is what fixed it 

I have several devices connected via wifi and one (my main server) connected via cable ...

that server is Linux and was causing issues (most likely) .. when I unplugged the cable and connected via WIFI it started to work without any issue .... I tried another cable and it worked fine as well.. so most likely some "faulty" cable .... 

I read somewhere (during the investigation) that that server could have been sending something to that router (don't ask me) .. or by a faulty cable .... the latter one proved to be the culprit ...

try unplugging all cables and disconnecting all devices ... if it's stable .. try adding devices one by one ...