port-amd64/51134: Random shutdown (power button pressed) inside VirtualBox 5 on Windows 7

[tomas.t.bodzar%tieto.com@localhost]

>Number:         51134
>Category:       port-amd64
>Synopsis:       Random shutdown (power button pressed) inside VirtualBox 5 on Windows 7
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 13 09:55:00 +0000 2016
>Originator:     Tomá? Bod?ár
>Release:        7.99.29
>Organization:
Tieto Czech s.r.o.
>Environment:
rumpbase: {1} uname -a
NetBSD rumpbase.x.x.x 7.99.29 NetBSD 7.99.29 (GENERIC.201605120350Z) amd64
rumpbase: {2}

>Description:
When logged in NetBSD amd64 7.99.29 running on VirtualBox 5.0.20 r106931 via Putty 0.67 from Windows 7 then after sometime (random) NetBSD shutdown and message on console says that "power button pressed".
>How-To-Repeat:
1. Install VirtualBox 5 on Windows (7 at hand right now) including extension pack, Windows 7 set to balanced power mode and connected to AC (Dell Latitude E5540)
2. Download amd64 NetBSD current iso
3. Install NetBSD in to VirtualBox as full install
4. Config dhcp network
5. Enable sshd, ntpd
6. add one user as member of wheel group
7. Start NetBSD
8. Use Putty for connection to NetBSD
9. Start tmux (tried with 3 tabs sessions)
10. In one session su - to root
11. In other 2 regular user with csh shell
12. Do some random work with any commands
13. After some time you will get message "power button pressed" and system goes down
>Fix:
N/A