Router speed capped at 500 Kbps when connected through LAN port

Question

I have recently brought a xiaomi router 4A gigabit edition (Global Version). I am connected to my ISP using PPPoE with a 5 Mbps connection. I am getting the correct speed on WiFi but from my PC which is connected with this router the speed gets capped around 500 Kbps.

There was no issue for this same setup (using the same cables) with my old TP-Link router. Moreover, when I connect this new xiaomi router from my office there is no speed issue. The ISP of my office connects through DHCP.

Any help would be appreciated. Thanks.