I had a similar issue! I fixed it with a new LAN cable I bought from Amazon, the one they supplied just wasn't cutting it for some reason, faulty maybe? But try a new LAN cable from modem to router and test. 

  @Kumpel Hi, thanks for the detailed info.

Since you’re using the Archer BE550 (V2) and the issue affects both Wi-Fi and wired devices, this points to a WAN/ISP-side disconnect, not a wireless problem.

The log Led Controller INFO – INET_OFF typically means the router detects the internet connection dropped on the WAN port.

Here are a few things to check:

1. Bridge Mode – If your Technicolor device is still acting as a router, double NAT or conflicts can cause brief drops. Set the modem to bridge mode if possible.

2. WAN Settings – Confirm the correct connection type (DHCP/PPPoE/VLAN) is configured exactly as required by your ISP.

3. Replace Ethernet Cable – Try a new cable between modem and BE550.

4. Firmware Reset – After firmware updates, a factory reset + manual reconfiguration can resolve stability issues.

If the old combo modem worked fine, the BE550 may be more sensitive to line instability—like a Night & Day Emergency Dentist that immediately reacts when something isn’t perfect 😄

If the issue continues, please confirm:

• ISP type (Fiber/DSL/Cable)

• Whether modem is in bridge mode

• System Log entries right before INET_OFF

That will help narrow it down further.