Adobe has been replacing uploaded keywords on some images with generic and often incorrect keywords. I have to fix several images where the keywords were uploaded in exactly the same way as other images that were not affected. Replacing keywords is a VERY painful process on this site, as they have to be replaced one-by-one.
I'm developing a theory about the pattern, since not all images are affected. In the cases where keywords were replaced on my images, the original set of keywords contained one or more accidental duplicate keywords. Other sites will automatically remove dup keywords. I haven't confirmed by checking for the absence of duplicate keywords on images where the original keywords were preserved, though.
Even if this is due to duplicate keywords, it's obviously the wrong way to handle it and constitues a bug.