@GuiPoM 

1. Unplug Ethernet cable from both ends, then plug it back. That simple trick helps sometimes.

2. If it did not help, replace Ethernet cable.

This is what may have happened: your cable is in sort of gray zone, where it is not completely dead but has some issues. On restart, Satellite Deco establishes Ethernet backhaul. Then, transmission errors over the cable start to add up, that forces Satellite Deco to abandon Ethernet link. Transmission errors happen when cable has issues or is layed near something that emits strong electromagnetic interference.

Hi @Alexandre. 

The problem is not to temporary fix the issue, as unplug or rebooting helps.

But there must be a regression in latest firmware for BE85.

It has been working perfectly fine for months, not to say years with my previous X90. The best solution would be to disable the wireless backhaul, I don't want it to trigger at all, it should never be used when wired. It acts as if the wired wan stops working.

Again, I am quite confident I have no hardware issue with my wall cable as well as my switches or patch cables. There was no issue at all and it started behaving strangely on my side since last firmware update.