Open Radar

 
Summary:
Manually syncing media to an iOS device will sometimes hang on "preparing to update". When this happens, the media is not actually copied to the device, but may increase the value of space occupied by the corresponding media. Deleting the entries (greyed out with dotted, outlined circles) does not always decrease the listed capacity. This is also usually associated with all media disappearing from the device, though it is still displayed through iTunes. Sometimes the capacity of "Other" increases by the amount of the missing media. Only restoring to factory settings can completely clear out the missing data.

Steps to Reproduce:
Connect an iOS device to iTunes.
Manually add a collection of media to the device by dragging it to the iTunes window.
If the transfer hangs on "preparing to update", quit and restart iTunes. Sometimes the transfer just ends without actually copying anything.
At this point, if the issue is occurring, the media entries will be listed in grey with dotted circles.
Deleting these grey entries may or may not actually free the referenced space on the device.
At this point all media on the device is usually missing.

Expected Results:
The transfer should either complete successfully, or fail without taking up space on the device. Additionally, a successful or failed transfer should not wipe existing media from the device.

Actual Results:
Media is not transferred and appears grey in iTunes. Existing media is hidden on the device, but still takes up space on the device.

Version:
Mac OS X 10.10.2 (14C109)
iTunes 12.1.0.50

Configuration:
Specific triggers have not been identified.