I have a number of Raspberry Pi Model 3 B+'s and they all have the same problem with SSH, when i connect it will randomly freeze. Sometimes this happens after a few seconds but occasionally i'll get a longer stable connection. The PI's are all connected over Ethernet and are all running the latest version of Raspbian Buster Lite. The PI itself continues to run fine and i can reconnect however the session will then freeze again. They're all network booted but this also happens when booting from SD card. The terminal software i'm using is working fine otherwise and i can get a perfectly stable SSH session on a Debian or Centos VM so this is limited to issues with the PI's only.
Its very frustrating as i can barely do anything before the session freezes so things like Screen aren't really much help when i often only get a few seconds of usable time.
Version details from uname -a are Linux raspberrypi 4.19.85-v7+ #1279 SMP Fri Nov 22 15:41:04 GMT 2019 armv7l GNU/Linux
I've tested the MTU and the path from client machine to the PI has an MTU of 1500, ping -M do -s 1472 ipaddress gets a consistent response so this doesn't look like an MTU issue