You may read my post How to find which ESXi 5.1 host lock the VM, it’s a solution to figure out which host lock down a file.

But sometimes you may face similar problem but different solution.

You are able to browse the file by CLI or GUI, but cannot delete by either way. It returns you device or resource busy or similar error messages.

You could try following command to delete the file/folders:

rm [File or folder name] -rf