Pictures sometimes give a false impression from lighting or angle, but I tend to agree with the previous guesses at the cause.
Looking at the picture of the chamber, it appears that the combustion deposits on the plug side of the squish area are about the same color as the exhaust valve. This indicates heat. The exhaust valve is very commonly that light color, because it's the hottest spot in the combustion chamber. If the deposits in the squish area are actually that color, and got that hot, then that is very likely a cause of this kind of trouble.
Looking at the picture of the piston, it seems that there is no clear indication about where the squish area was, and the deposits appeared to be evenly thick all around and almost to the edges, except for the area under the intake valve at the perimeter of the intake side, which seemed to show indications of fuel wash.
Both of these pictures seem to show indications that the "squish area" is not functioning as a squish area, but is apparently just there "for looks" or something. It's not making any squish, or it would look much different in those areas which were providing squish/quench. From those pictures, and the thicknesses of the deposits shown, it looks to me like at least 2mm of deposits on there, which would indicate that the squish zones are beyond the definition of a squish zone, and if they are like the UCE engines that we have looked at, then they have more than .080" of distance from the flat areas of the cylinder head. Interestingly, it is a known phenomenon that when the squish distance is opened up beyond .060", but less than .100", then that INCREASES the likelihood of detonation occurring, instead of decreasing it. This may be what we are seeing here. If you open up the squish beyond the .060" limits, then you should open it wider than .100"-'130" to avoid having potential detonation effects from the danger zone. Either be in the squish parameters, or be far out of them.
Giving the RE engineers the benefit of the doubt, I would have to guess that they had squish set, and the local fuel supply could not tolerate the compression amount which resulted from this, even with the squish, so they backed-off the deck height with a minor change to the barrel height machining, and thus reduced the compression without a re-design of the piston or chamber. Either they didn't know about the danger zone, or it was deemed to be necessary to set the compression height there by the bean counters, and hope for the best.Perhaps in India, this doesn't come up as a problem with low speed running that is prevalent there. However, for export models, particularly in Australia which has become the world leader in killing Bullets, this might not be so good for the riders there.
This is why we will re-set the compression height for the piston for the UCE that we make at Ace, and correctly meet all the other necessary parameters, and this is why I have repeatedly mentioned this subject in previous posts about the UCE and the piston and compression subjects.