Bug report: disappearing previews

Just opened an old gh file with the latest GH version, to edit and renew, which involved some not so heavy computing for my rig, and when i am replugging the wiring, the preview in rhino viewports would totally disappear. Happened several times, this problem can only be solved by save, exit and restart Rhino and GH. And sometime I get a recovery file notification. 

This problem never happened in previous version, so I presume it's a bug caused by the latest update.