Lost connection to WAN

Hello,

I'm using a TP-Link Archer C7 v5 with OpenWrt (18.06.4). Few days ago it suddenly lost connection to the WAN, and regained it only after factory reset. Now this happened again, but nothing helps, not even a factory reset. Any ideas what to try next? Or could it be a hardware problem?

TIA

could be, but I'd try a firmware update 1st.

Upgraded to latest, no joy.

Thanks.

does dmesg reveal anything ?

try ssh to it, and run a continuous ping session towards 8.8.8.8, to see if the connection actually goes down, or if it's something else.

Why don't you try using one of the lan ports as a wan?

I didn't even know it was possible. Anyway, that didn't work.

Ok, new thing: pinging from the router to 8.8.8.8 works, sort of:

28 packets transmitted, 8 packets received, 71% packet loss

Pinging from the PC doesn't work at all.

Please apologize for the very basic question, but have you tried to replace the CAT5 cable you use to connect to your WAN port?

Yes. I also connected my spare router to same cables, which works fine.