I found the issue :-)
I used another ssh client and it worked fine. The issue with the ssh client that caused the switch to spontaneous reboot seems to be in my ".ssh/config" where I use "RemoteForward 52698 localhost:52698" for my rmate editor.
If I ignore "RemoteForward 52698 localhost:52698" then I have no problem with ssh login.
What I know of is that this issue has affect on version YA_16_06_0006 and YA.16.04.0008 - so maybe from version YA.16.xx
There is no issue in version YA_15_17_0009.
I would suggest that the switch should just ignore ssh RemoteForward like most other equipment. I think it's rather critical that somebody malicious or by accident can bring the switch to spontaneous reboot?
Can somebody comment on this?
Cheers, Martin