I would suspect some conflict with a misbehaving app or utility.
Yesterday I wrote a topic on the Abode community:
It looks like we have the same problem with the hand tool. Perhaps OS Sierra is the problem. I bought my iMac with El Capitan 2 months ago and haven't had any problem then. Off course I can reinstall my computer, but I think I can assume that Photoshop should be working fine on Sierra as well, isn't it? Perhaps we should wait for an update of PS or is there another solution for this issue?
Thanks for your reply. Siri is disabled since I upgraded to Sierra. That's not the problem I think. I have been in contact with Adobe again and probably this bug is caused by the Wacom Bamboo Mousepen. I wrote Wacom an email to see if they have a solution. As long as the Wacom is not connected to my computer and I only use the Apple mouse, there's no problem at all.