It seems to be a pretty nebulous bug. I've seen a few posts about it on the forums (usually folks using Wacom tablets), but it doesn't seem to be affecting everyone who has a tablet.
I would recommend filing a bug report and being as specific as you possibly can about what software you have installed, what other hardware you have installed, etc. because this seems to be one of those bugs that's really hard to pin down.
This is a problem I'm also having outside of AE 2014. Throughout OS X 10.10.4 every now and then I had this sticky pointer syndrome. However it wrecked most havoc when in AE when whole groups of keyframes would change position without me noticing it. Now I'm on 10.10.5 and we will see if thing have normalised. Also - check your Wacom driver.
MacBookPro 10,1 - OSX 10.10.5 - 16GB RAM - AE 18.104.22.168 - Wacom driver 6.3.11w3 (Intuos 3)
Thanks for your reply Szalam - The thing that gets me is that the problem is only really bad in After Effects CC 2015. Other programs (even Adobe After Effects CS6) runs fine without the click and drag problem.
Thanks for the reply Mr.K8 - I have the lastest wacom driver installed. The only time I have the problem is in Adobe After Effects CC 2015. All other apps including Adobe After Effects CS6, the issue doesn't occur for some reason.