It is very common for an operating system upgrade to break the AppleScript in a Mac app, especially an Adobe app, which is primarily a cross-platform Adobe app and only a Mac app as an afterthought.
If you are compiling the same AppleScript code on different versions of OS X, you are using a different version of the AppleScript compiler in each case, and therefore you are going to see different bugs as the different compiler interacts with the same AppleScript code and the same Photoshop 2014.
