Problem with Fujitsu PR09

[gavod]

Hi.
This port replicator is driving a LG 4K monitor using DisplayLink from a Laptop running Windows 10.
There are also USB connections (e.g. keyboard and mouse) and ethernet.
All goes well until at some random time, usually when I'm doing something involving the network but I can't be certain of that, the cursor gets sluggish and the cursor graphic doesn't change as it's moved across windows etc. Eventually the network icon changes to indicate that the internet is unreachable and the laptop display comes on, which I guess is when the laptop thinks it no longer has connection to the monitor.
I have discussed this with Fujitsu, we have checked that firmware and drivers are up to date and they have sent me another PR09 to try. This is slightly more reliable (it lasted half a day at first) but it exhibits the same behaviour. If I move the ethernet connection from the PR09 to the Laptop the problem seems to go away; and it also seems to be ok if I plug a ethernet cable into the laptop (in addition to the one in the PR09). So I don't know if it's a network problem that's triggering the failure or if adding the ethernet connection to the laptop simply takes sufficient load off the PR09 to mask the problem.
I switched on logging (including network, in case it's a network issue) and it ran for ten minutes or so before it failed. Once it failed, I gathered the log files, which I have attached. Whilst I was gathering the log files I thought something else had gone wrong as it got to "Gathering netstats" and sat there for more than 10 minutes so I unplugged and replugged the USB connection between the Laptop and the PR09. If this has made the log files unusable please let me know and I'll try again.
The whole point of the setup was to require only a single connection to the Laptop when it's driving the 4K monitor, so having also to plug in an ethernet connection is a major irritation.
Any and all help or suggestions appreciated.