Some time ago there was a bug that caused all Ethernet ports to operate at 100Mbps speed if a single port had a 100Mbps device connected.
This issue was solved later, but now I believe it is not actually fully resolved.
The long story short is that I had one 100Mbps device (a Samsung TV) connected to one Ethernet port, and all other ports had Gigabit devices connected.
Everything was working fine (or I thought so).
The issue I discovered is that every time there is traffic on the 100Mbps port, it causes packet loss on the other Ethernet ports (I discovered that whenever someone was watching Netflix or other streaming service on this TV the other Gigabit devices connected to the remaining Ethernet ports experienced about 1% to 2% packet loss).
I just disconnected the TV from the wired port (now I am connecting the TV via Wifi) and the packet loss on the Ethernet ports are gone.
I will not have time to investigate this further, but at least in my case I confirmed that connecting a 100Mbps device to one of the Ethernet ports will cause packet loss issues on the other ports (whenever there is traffic on the 100Mbos port).