I feel bad for the people on the Jubilee line this evening stuck between West Ham and Stratford for what looks like 2 hours(+), not going anywhere due to a line suspension / customer incident
(after a while, another train showed up, perhaps to assist in rescue or something)
so, Jubilee line trains apparently can lose their air pressure or something like that (?) very rapidly after an unexpected loss of power, and I think there's some procedure the driver needs to carry out after such a loss to ensure the train can move again
I wonder whether what happened was the train didn't get that done to it, and is now just stuck in place until they figure out how to shift it
I have no clue what the problem you're describing could be there, but this reminded me of very old DMUs that did have such a problem: they needed air pressure to engage or disengage final drives (in forward or reverse), and they couldn't be towed with them engaged (because that would damage the gearbox that was receiving no oil flow). See https://www.youtube.com/watch?v=XCQKvEy6jVs for a description of that ancient train's failure modes.
