Nikon Df hangs while transferring NEF file

[bnk]

Greetings.

I'm using qDD 3.5.3 on an iPad Pro running iOS 10.2.1, together with my Nikon Df and a WU-1a wireless adapter.

The Df has a SanDisk Extreme Pro HC I micro SD card (with SD adapter) installed, which contains about 550 NEF files shot on the Df.

When I try to view the contents of the Df's micro SD card in qDD, the initial transfer of preview thumbnails completes successfully. However, when I tap a single thumbnail, the transfer of that NEF file to qDD hangs. The media access LED on the Df turns on and initially blinks rapidly, and the progress bar in qDD progresses to 5%. At that point, the media access LED on the Df stays lit but stops flickering, and no further progress in the transfer is made, until after tens of seconds, there appears to be a timeout on one end or the other, the LED goes out on the Df, and the connection between qDD and the Df is broken. (I verified that the iPad is still associated with the WU-1a's "AP" at this point, so the problem isn't a disassociation between iPad and the Df.)

Do others see this sort of behavior when transferring NEF files with Nikon cameras (or raw images with other makes of camera)? Is it possible that this hang is a manifestation of a bug in qDD? Or is the WU-1a and/or the Df firmware driving the problem (and thus unusable, regardless of the software on the other end of the WiFi link communicating with the Df)?

Thanks very much,
-Brad

[hubaiz]

Is the 'Load image infos for images already on camera SD card' qDslrDashboard option enabled?

[bnk]

Is the 'Load image infos for images already on camera SD card' qDslrDashboard option enabled?

No, it isn't. But I use the "reload" button in qDD's image viewer to trigger transfer of thumbnails from the Df to qDD, before I touch a thumbnail (after all thumbnails have transferred) and encounter the hang I describe above.

Should I enable this preference--should it make a difference in the app's behavior vs. my manually "reloading" the images on the camera from within qDD's image viewer?

Thanks,
-Brad

[hubaiz]

No, the option if enabled will load the image infos after the connection is made to the camera.
Eventually check if the 'Use Nikon high speed transfer' option is enabled/disabled and try changing it.
Can you try with an empty SD card, does that work?