Now, the last step is to unhook the two halves of the metal chassis from each other - with the correct motion, this happens very easily

Firmly press on the top half (the bottom has the PCB laying right against it) whilst prising with a flat-head screw driver at the seam: there's 3 metal clips to unhook on each side

And you're done !

Feel free to share what problem yours had and how you've fixed it down in the comments :)