Win 7 pro
Broken: ( 2.74 , 2.76.1 bfdb420)
Short description of error
strange behaviour of correct Uvs while sliding a vertex. when you slide (GG)selected vertex ( or other) to right, left or top , then check one of the options on toolshelf (i.e. correct Uvs). Instead of staying where you moved this vertex, it moves always down. It does not happen with two vertices selected.
Exact steps for others to reproduce the error
slide (GG) selected vertex to right, left or top , then check one of the options on toolshelf