Thanks for that torch1! However, that doesn’t apply to me, because my vr600 is not plugged in directly to the internet, it represents a segment of the network, so ipv6 is deactivated in the internet end, but on lan i’ve got the RADVD option selected from the last screenshot on that link. As to a need for ipv6 - no we certainly do not need it, it is just enabled and supported by every other device, so it would be fair to expect a major manufacturer to support it out of the box too. 
@komuva i guess you have tried recommended troubleshooting steps? because for me to come here is the last resort, it means nothing out of standard works - like changing ip config, resetting wd, playing with network config etc
Have placed wd my cloud into a different segment on different router with ipv6 explicitly disabled - same thing, i guess it’s wireshark next for me…
Is that a realistic statement?
I believe that the WD MyCloud software predates IPV6 protocol.
I don’t think WD has been adding “features” to the code after product release - - > only maintenance patches.
If I recall correctly, I believe my EX2 Ultra has explicit IPV6 support, but my MyCloud box does not. Either way. . . I have ultimately had to disable the IPV6 functionality on my PC’s to get it all to work after either the Win10 1903 or Win10 1909 (I forget which) update. It required a few days painful trouble shooting to get to that point after that updated caused problems on two machines at home.
An IP addressing issue could DEFINITELY be the problem here, but to me it sounds more like the My Cloud is ‘crashing’. Possible causes could be bad RAM or Flash memory on the control board, that the last firmware update glitched, that the control board is overheating, or that the power is unstable due to a problem with the adapter (likely a bad capacitor).
I would try: 1) blowing it out with compressed air, 2) another power adapter {12V 1.5+A}, 3) reflashing the firmware, possibly going back to an earlier version.
Getting back to IP addressing tho, I think you need to take a long hard look at how your network is set up. If you are connected to the internet (sounds like you’re not) then you ABSOLUTELY should be using a router. If you have a router (with Internet or not) turn on the DHCP service on the router, and off on the computer(s). If you have no router (because you’re not connected to the 'net) then you should be using static/fixed IPs on all devices (computers and NAS), preferably on the 192.168.1.x subnet.
If Windows isn’t set to a static address and it can’t find a DHCP server, it defaults to a 169.254.x.x range with the last part being randomly chosen. This is problematic for many reasons and should be avoided.
