That is the part I am wondering (and worrying about); the missile has over-ride controls to allow it to be remotely destroyed. Why was that not done?
It is possible that the bungling extended to this failure as well. Oscar's First Second Law applies.
Sir, the chances are remote that two failures will happen concurrently. I will allow that the missiles brain got fried & that could mean all sorts of things going wrong. But in sensitive systems there are back-ups & fail-safe modes. If there were none then this is not only a bad design but a security blunder of the highest order in a key system.
We must consider the counter-point that there is an element of mischief involved here. Let us explore a likely scenario:
On the day J-10CP is being inducted, Indian forces decide to conduct a test of supersonic missile close to Pakistan, to send a message. So there is already an issue with intent here. Next, the missile goes rogue in a precise manner. It crosses the border at what appears to be a right angle which gives it a chance of maximum range inside Pakistan (surprise, surprise), all the way to Mian Channu and exactly on the left side of the most important highway. Coincidentally, the missile did cross the most important railway line as it crashed.
The timing, the symbolism of the main highway & major railway line, crashing into the heart of Punjab, the fact that it went straight at a suspiciously optimum angle, the lack of any fail-safe system, & the lack of self-destruction all point to a malicious intent. You would have to excuse me in thinking the worse of it.
It would be right prudent of you to consider the presence of a rogue element within Indian forces - highly likely in the supercharged communal & anti-Pakistan atmosphere. Or else the intent was always there & the launch was according to a preconceived plan. Had Pakistan intercepted the missile via (say) HQ-9, the missile would have been blown to smithereens & India would deny that they did anything wrong because who would believe in tiny bits & shards to make a case for a rogue Brahmos?
It would in fact be a better option to believe that some rogue element did this, than to believe that a whole weapon system is badly designed with a fatal weakness, or that Indian decision-makers are such reckless bunch that they would risk starting a war. The first option is easiest to fix of the three, I believe. So do not just dismiss it out of hand.