Kinda hard to tell with the pictures, but that's some surprisingly low quality solder work. I'm sad to see that on such an expensive set of headphones.
it may look a bit sloppy and burnt, but the actual connection looks solid without residue so its the connection that matters..
Also they used quality solder..
Also opening these units is not hard you just need the right type screwdriver and need to peel the pads off gently to gain access BUT,
Like I say, the main problem is the pads that will loose their bond so will need to use a double sided tape and the one I posted earlier is the only one that worked for me..