@Icecooll Please tell me what the connection error is,wireless drop,wired drop,or both? You can refer to Troubleshooting: Unstable wireless connection on TP-Link router Try to Change the channel and...

@Dijin Are the MAC addresses displayed on the Web the same as the MAC addresses displayed on Tether? Maybe you can change the device name in Tether,refer to How to change device name on Tether App |...

@robgon99 refer to What are the most frequent asked questions about the TP-Link devices' speed? If this article is of no use to you, try to reset your router

@praveenpivot Try with another Cat5e/6 cable or change the port of your ISP device. Try to reset the router to the default factory.

@Digard Maybe you can change the LAN type from Smart IP to static IP

@Vivek1998 refer to What should I do if I cannot access the internet through Wi-Fi router? | TP-Link Troubleshooting: Unstable connection on the TP-Link router