After more than 1 year, my deco M4's ethernet port keeps switching to 100 MBPS instead of 1000 MBPS.  Sometimes restarting the deco will restore the 1000 MBPS link but after a few hours will switch back to 100 MBPS.  I have a PC that is connected directly to my wifi router ethernet port and it stays at 1000 MBPs.  Is there a way to fix the port speed to 1000 MBPs and disable autonegotiation?

The exact model of my Deco M4 is Deco M4R(US) Ver. 3.0

My wireless wifi router is a Huawei HG8145V5 H/W version: 15AD.A S/W version V5R019C00S105 and my ISP is Globe in the Philippines.