iMac 10.12.2, GTX 780M. Running current CC 2017, Camera Raw 188.8.131.522. All drivers and CUDA updated. Use Graphics Processor is ticked. When I open ONE CR2 file in Camera Raw, scrubby zoom works fine. When I open TWO or MORE CR2 files, scrubby zoom is disabled. What gives? So frustrated.
Same thing here with Windows 10. It's as if it is trying, but not quite making it. Fine with one file open. It breaks with two or more.
I left it for a while in case was busy building previews or some such house work, but it made no difference. I actually had to re-enable GPU in ACR Preferences to test this, as it tends to cause other problems for me, but I'll leave it turned on for now. Unfortunately I don't take a lot of pictures nowadays (I work from scratch) so issues might be a while in showing up.