Ever since Lightroom CC 2015.7 there has been a performance issue with Lightroom and Sony ARW files. When working in the develop module, when you first move to an image, the sliders will operate, but have no effect for several seconds. On non-sony images this does not seem to be a problem. This issue only started with 2015.7 and has not been resolved by subsequent updates. In some cases it can take up to 10 seconds after an image loads in the develop module before the sliders become responsive.
I have tried using a new catalogue with no other images in it, to see if it was my catalogue, but to no effect. Others have reported this too, but as they are not using other cameras, they did not realise it was specific to sony ARW files. One user posted a video on YOu-Tube showing the problem.
This is not my video, but the person is having the exact same problem that I am having.
My setup is a MacPro 12 Core with 20GB ram. I've also tried it on a retina MacBook pro and the delay is not as much, but it still exists. The only solution seems to be to wait for a few seconds each time you move to a new image in Lightroom.
There was also some suggestion that it could be related to applying presets, but it seems to be affecting me regardless. It does seem to be less of a delay if you don't apply any presets though, but it's still delayed compared to using non-sony files, or the performance pre 2015.7