Tethering Issue's Nikon Lightroom CC

Hi,

I have been tethering with both a Nikon D610 and D750, after about an hour the images stop transferring, the transfer bar appears in the top left but doesn't fill up the image actually does appears but without the adjustments of the previous image and and i symbol in the corner and the bar stays in the top left and remains empty. I have to quit lightroom and it says "there is an image transferring would you like to quit". I restart lightroom and begin tethering again but the same thing will happen around half a dozen times during the day. I have deleted preferences so that's not worked just seeing if anyone has any other ideas?

Cheers

Rob