Here's what I'm doing:
- open a Finder window with source directory (500+ files).
- open another Finder window with target directory.
- select all files in source directory using ⌘ - a
- grab selected files and hover target window
- press ⌘ so files are moved instead of copied
- release mouse button
But only cca 85 files are moved. Rest is left in source directory (while still selected). The same happens when copying files.
Is this something I can change (number of files moved)? An error/bug? Some app interfering with drag & drop behavior? I'm left with using Terminal to move my files, which besides being annoying isn't really possible when file selection is not a simple ⌘ - a.

Each "drop" moves ~85 files, i.e. I have to do the "drop" again to move the next batch. When copying, same first ~85 files are "selected to copy", i.e. I'm asked if I want to overwrite files in target dir.
– Martin Tóth Aug 17 '15 at 08:54And in Finder, I am only able to drag and move/copy 86 items. I can select more but when I drag them to a new folder or other location the most that will get moved is 86.– IconDaemon Aug 17 '15 at 10:49