Hi 
It’s interesting you bring this up because on my previous install I had a feeling it might have something to do with this. I do mount NFS shares using autofs which may very well be the culprit. Maybe I can change something concerning autofs behaviour. I am using a pretty fast wired connection so for the moment I don’t suspect this to be the cause.
This is within the Plasma system settings GUI app, right?
Edit: I found the setting regarding recently accessed files but I don’t understand what exactly you mean by session management. Did you set “Start with an empty session” in the “Startup and Shutdown > Desktop Session” section?