Fisch, you're making us look bad, man! You know I tested every one of those strips we sent you, personally.
You've got to change your attachment plan here:
Those steel bolts and hard nuts are shorting out the LED circuits (traces) underneath them, plain and simple. If the nuts aren't crushing them, the threaded bolts are cutting into them. It's that simple. It's the same issue you had with the first strips, and it has the same solution: replace your attaching hardware with nylon bolts, nuts and washers of M3 size only. With any luck, you won't have permanently damaged most of the traces, and many of the strips will light evenly.
Or just use double-sided thermal tape and forget the screws. Either way, the steel needs to go. You are killing your strips, and causing a dangerous safety risk to yourself by shorting those strips to your lamp frame. Please add a ground to your frame if you haven't already.
You've got a beautiful rig, I hate to see it not working properly. Please take my advice on the screws, once and for all. No one has had the extent of issues with dead circuits that you have had, and in the two other instances where it occurred, nylon screws fixed it instantly. -b420