TP-Link Archer VR2800 Disconnection Problem!

I trusted TP-Link quality and bought one of the most expensive modems, the VR2800. After using it well for a long time, it broke once or twice,  I updated the Firmware directly from the modem's interface and the situation did not improve. Technicians from Telekom came and examined the line, no problem was found. I reset the modem to factory settings and reinstalled it. But it constantly disconnects at least once a day and does not recover without turning the modem off and on by pressing the power button!