WTF happened to The BMJ?

The BMJ recently published an “exposé” by Paul Thacker alleging patient unblinding, data falsification, and other wrongdoing by a subcontractor. It was a highly biased story embraced by antivaxxers, with a deceptively framed narrative and claims not placed into proper context, leading me to look into the broader question: WTF happened to The BMJ? (Updated and revised from a week ago.)