FWIW, I have also created another sharing directory using the built in memory, and it works normally. So, it seems to be purely an SD card related issue.
I'm having the same delay issue (Blackberry DTEK60, Android 6.0.1). I found that if I cycle Selective Sync the file will appear quickly. What I can't seem to do at ill is rename a file. It simply does not save the changes.