1. Debian Stretch Host OS.
Guest OS doesn't matter, in KVM i get kicked always, in virtualbox it's random. Sometimes I get kicked in few minutes, sometimes is okay for ~30min.
2. 4.9 is okay
With 4.15. 4.16 4.17 i have this issue
3 and 4 Here all is okay, because with 4.9 all is okay.
5. Yes...