Host Win 10 1809 64bit
Guest Linux Fedora 29
Intel i7-6700 16gig memory
After an import appliance completed vbox stopped. No messages or warnings. Since there is only the one vm in the setup no other vm was impacted. Vbox started back up without problem. After an uneventful session using the vm I closed it down and then proceeded to shutdown the PC. Whereupon Windows displayed a message that VBox was still running, though Windows allowed me the option of choosing to terminate the stray Vbox session.
The file for the import was made by a v5.2.20 on the same machine under a different partition. It is 5.7gb in size.
I do like the new import option to change the input file format to VDI. A nice touch to v6.0. Thanks.
JC