Nikon D5 - Manual (Page 288)

266
I
A
Voice Memos
Changes to the protect status of images also apply to any voice memos
that may have been recorded with the images. Voice memo overwrite
status can not be set separately.
A
Removing Protection from All Images
To remove protection from all images in the folder or folders currently
selected in the Playback folder menu, press the
L (Z/Q) and O (Q)
buttons together for about two seconds during playback.