MacBook Pro brings down ethernet network when idle

This is a symptom I have struggled with for about a year now. Here's my setup for background:

• MacBook Pro (15-inch, 2017) running macOS Big Sur (11.1) - I saw this with macOS High Sierra as well
• MacBook Pro connected to Lenovo ThinkPad Thunderbolt 3 Dock
• Wired Ethernet on the other side of Dock connected to Synology Router RT2600ac running SRM 1.2.4-8081 Update 1
• Other computers, TV, NAS, IP phone devices connected to the the wired network either directly to the router, or via switches

When I leave the MacBook Pro connected to the Dock and let it idle for some time, very often, I see other devices on the wired network stop working (ones on WiFi work fine). The TV stops streaming content, NAS goes offline, IP Phone disconnects. The DS router app, which is used to manage the Synology Router, shows 0 devices on the wired network. All indicating that the wired network is down.

When this happens, I simply unplug the MacBook Pro from the Dock. In seconds, things get back to normal, with Ethernet network working fine on all devices. I can re-connect the MacBook Pro to the Dock and begin working again.

This does not happen when other devices are connected to the Dock and they are idle. That is why I thought I'd start with this forum. I am at a loss on where to begin debugging this. Not sure where the issue lies amongst all the parties involved.

Any ideas? Suggested remedies? Has anybody else seen something similar?

Thanks in advance.