Ok, I think what's goin on is from the machining it left a bump up in the middle - is that correct? This is quite common, unfortunately, least in lights I usually mod (the lower end, budget level). You will never find that in some brand lights I'm sure - probably true for MaxToch.
You can usually spot them easy - sit the MCPCB in there and see if it wobbles or not. If not, there could still be a depression in the middle, so still have to check for that. If there's a good grease under the MCPCB, the MCPCB should be suctioned to the shelf surface so you have to pry it off. If there's no suction, there's probably a contaminate in the way or something is not flat.
Not surprising at the prices Sofirn charges, also it's been so common in China for initial batches to be superior quality, then later batches drop in quality - just how they do business unless you really stay on top of them.
Brass P60 pills for example are known for this. With those I would take a large nailset or punch and give it a couple taps of the hammer and could flatten them out every time. Easy way to check is a metal flat edge, like the end of a small SS ruler - I use one often to check for flatness. For these SP70's, I wouldn't hammer. Most alum shelfs I'll sand it out, starting with maybe 200-300 GRIT paper. Lot of times you can see that middle point go down and down, constantly checking with the flat edge.
It's just something I always do when modding. Got to take out that MCPCB and discover what's underneath - many times there's surprises like a fragment of solder stuck - they don't check, they don't care. Do you think Convoy's are made and assembled by Simon or Emisar's made and assembled by Hank? Nope, so do those workers care as much as Simon or Hank? Nope.
PM'ing with Richard at MtnE in the past, wow, nightmare's of entire Convoy batches messed up. People wondered why he didn't stock this or that, and many times the lights and parts came in but had to be rejected - he would not sell them in that condition.
I feel for you. I toy'd with the idea of goin retail or modding at a more serious level many times (even had a job offer to mod!!), but having to deal with the mystery of what you'll get to resell is scary, plus the time/work to make it right -- I'm too much of a perfectionist to make money at this.
I thought the SP70's were aggressively priced more recently. They could do the shelf right but I'm sure it takes more time/labor and these workers are under great pressure to produce.