Files windows blank. Connecting a runtime to browse,

[flydragon2018]

Describe the current behavior
the file windows becomes blank.
Describe the expected behavior
File Explorer should show the directories and files

What web browser you are using
Chrome

Additional context

notebook status is "busy"

[craigcitro]

Can you provide repro steps? We have at least two reports, but I can't manage to repro the failure here, even when a long-running command is executing.