Thanks for you response!
Frankly, trying to remember what i need to do before closing the lid on my Mac is not something i would like to focus on :)
At this point, force quitting the client and then resuming the session is just as good.
I am trying to keep track of this and I dont think it is time related anymore. Sometimes, it happens after the computer sleeps just for a few minutes and other times doesnt happen after the entire night.
This could easily be something with virtualbox networking, but regular ssh sessions survive it or reconnect seamlessly.
Is there any logs that I should look at?
Thanks again.