Could someone help with a problem that I am experiencing, this router has been in use for about a year +

Three days ago ether3 started going down around the same time of day around 11:00-13:00

I am unable to find a cause, is not issue as I have found in the forums about ether flapping.

This is where the port physically goes down and then reconnects, all pppoe connections through that port drop, and port completly looses connection for a short period, then on it's own comes right.

If anyone can help, the only log entries is ether2 down then ether3 up, and then all the pppoe sessions going down and then starting up again.

I don't understand what would cause this, especially that it only happens at a certain time of the day, and only about once per day, for the last three days.