InDesign is constantly losing image links

My InDesign will not keep links to some images.  I am using InDesign to create catalogues and often have 1,000 images.   I am using Winodws 10.  All of the images are saved on a network drive with a mapped drive letter.  The locations of the images do not change and they are not edited in any way while my InDesign document is closed.   But when I reopen, I find some or sometimes all of the images have lost their links and I have to relink them all again to the exact same path/location.