I use PC a lot, in nearly all images. I use a very wide angle lens to photo murals and other artwork in spaces too tight for anything more than 12mm on a full frame sensor. No matter how hard I try to ensure sensor plane is parallel to my subject, I get keystoning, either horizontal or vertical or both. So, unlike when I was correcting for perspective back in the day when using a view camera, I have to rely on PS CC's perspective crop tool. I just experienced the terrible distortion I see occassionally when using the tool. I have found that if I am correcting more than one axis, I get huge distortion. I can always tell I'm going to get it because it takes a lot of time for the correction (or I should say the incorrection) to happen. And I have a new machine that's a rocket! Here's what I've found, and it has nothing to do with the the fix that's recommended here. If I correct for one side of my image, then the others individually, I don't get the distortion; I don't recall ever getting it when I do this. If, as with my last attempt, I correct for one side vertical and one side horizontal at the same time, it would yield the distorted image. And make me very angry! I got the huge distortion. Twice. Then I corrected the sides individually and no issue. Not a very good tool in my estimation. Adds so much time. And the correction in RAW processor is absolutely no good at all!! Photoshop, where the hell are you on this!!