Re: They just changed it this morning
I'll bow to the knowledge of someone who actually reads Russian, but according to Google translate, your link says:
“We are talking about damage to the end sensor as a result of unintended, but erroneous negligent actions of one or several Progress RCC specialists in the assembly and test building at the 112th site of the cosmodrome when assembling a package consisting of side blocks of the first stage and the central unit of the second stage. there could be a one-time single violation of the technological process, "said the source.
As a result, when this side unit was detached, the jet nozzle cover jammed to remove the side unit from the central unit.
ie the sensor failed, so the signal that the booster was detached was never sent, so the 'jet' (not an engine, it's a vent at the top of the O2 tank) that pushes the nose of the booster away from the core never operated.
The sensor didn't "snag" the first stage. It failed to operate because it was bent, so the necessary signal was not sent.
Of course, that all depends on your translation of that second and third paragraphs in the linked article, I'm not sure how many elReg commentators are bilingual in Russian?