That's a good question, "why did the previous crew put the train into emergency rather than a full brake application?
I'm assuming the dynamic brakes could not hold the train and as soon as the air was recovered the brakes released, with not enough time to fully charge the train line and the train moved out on it's own.
However a train left in emergency should not Bleed off in a few hours. There must be something else going on..
Question ....what happens to DPU units inside a tunnel? Do they stop loading, What happens to the dynamic brake on these units with loss of radio communications.