The RPi3B+ (and only 3B+) is a mess in terms of Ethernet networking. Even their engineer admitted it in their forums. The 3B+ can’t handle more than 100Mbps reliably (it is supposed to be able to handle 300Mbps on a gigabit port) and LAN is shared with USB, so when people try to use both at the same time they are not happy. Their engineers recommend connecting it to a switch with flow control enabled.
But… It can handle 100Mbps reliably just like the Pi3B. So, a simple solution is to restrict the LAN to 100Mbps. No need to fiddle with any obscure parameters. See my post in another thread on how to do it (last two paragraphs): Raspberry Pi 3b+ Clicking on USB Audio Devices Disabling the EEE reportedly helps but I am not sure it is necessary.