> This entirely fits a missed signal or a signalling/protection failure

Perhaps a signalling/protection sabotage?

> No official has hinted at foul play either

That doesn't really mean much. Officials in the UK are incredibly reserved in hinting at something that they can't back up with evidence. Since they're still investigating, they keep their mouth shut. But yes, the sensible thing is to wait for the report.

Why stop there? Maybe it's sabotage all the way down, like turtles?

I'm sure that even if the official report totally excludes the possibility of sabotage, for some people that in itself will be the clearest possible sign that there was, in fact, sabotage at play.