Moving files in Yosmite doesn't move all the files

I am having the weirdest problem since upgrading to OSX Yosemite.

If I select a bunch (hundreds) of files and try to move them to a different folder, only a few (under 100, like 86) of the files move. The rest are still left selected in the original folder.

I could not find anyone else experiencing this problem.

Anyone know what is going on?