I have a similar problem.
I've got 3x LS-WX4.0TL/R1-EU on my network (all delivered together). Two of the drives are working perfectly fine, the other one randomly drops off !
All three drives are setup identically apart from the IP address (all have their own static IP) with the same firmware. I've tried changing the ethernet cable, swapping the PSU and switch ports so I'm starting to think the drive may be faulty?
If I access the drive through explorer (so that I have entered the credentials) and then run the following batch file :-
:BEGIN
dir \\mydrive\myfolder /s
goto BEGIN
It will list the directories correctly for approximately 10-15 minutes, then start returning "The network path was not found". This will carry on until I reopen the folder in explorer (but it won't reask me for the credentials), then it will start to access the drive correctly again and start relisting the directories for another 10-15 minutes.
Any ideas? Thanks, Mark