This issue has been around for as long as I have been using SE.
I work in a Linux NIS/Clearcase environment. Certain directories (example: /vobs) take a very long time to list all the files. For example, if I type "/vobs" into smart open, SE freezes for a very long time while it tries to get a listing of all the files in /vobs. The same thing happens when I do "ls /vobs" at the command line. Even if I want to go to the directory /vobs/dir1/dir2, SE is frozen after /vobs for a long time, hurting productivity, even though I don't need a listing of the files there. My workaround is to usually type a junk character first, like s/vobs/dir1/dir2, then remove the "s".
It would be helpful if SE can enumerate the directory in a background thread or not freeze while waiting for the directory listing.