The file is okay and not damaged, as far as I can tell.
There are two easy ways two unpack .pck script files:
1. Extract the file with
7zip and add the file extension .xml to the extracted file. For this to work, the option to show file name extensions has to be enabled within your OS.
2. Open the Cat manager from the X3 Editor 2 (under Plugins). Under "File" create a new catalog (name and location doesn't matter). Drag the .pck script file to the now open window of your newly created cat in the X3 Editor 2. In the "Add Files" dialog, leave everything as it is (default settings should be "Compress: Check Compression Filter", "Compression: Automatic" and "If already exists: Ask") and press "OK". The pck file was now added to your cat. Now in the X3 Editor 2 click on the "Extract files" symbol. Select the destination location and if it isn't already, enable the option to "Decompress compress files". Afterwards hit "OK". At specified location, you will now find the .xml script file.
The first method is faster for single files. While the second is bit more complicated, but allows you to easily unpack a whole script package of pck files or all scripts from the scripts folder.