I witnessed an interesting occurrence the on DLR this afternoon.

I was walking across the footbridge to Custom House station, I noticed
that one of the new units (unit 105) was approaching with a Beckton
service. I was topping up my Oyster card on the new ticket machines
and I suddenly began to hear excessive brake-screeching from that
unit. I looked down onto the station and saw that all 4-cars of the
train had gone through the station. The train sat there for about
3mins, then the tail lights began to flash orange - which I believe
means that that the PSA has opened the train in manual-mode, it then
began to slowly reverse back into the station, it was berthed
accurately in the platform and it was tipped out of service. I asked
a passenger who was on the train what happened, the reply I got was
that it didn’t want to stop then the emergency brakes were applied
and it overshot the platform. I began to walk between stations and
another unit approached and stopped between Custom House and Prince
Regent and stood for almost 15mins despite the line ahead was clear
for it to continue, this began to create a back-log of trains heading
towards Beckton. By this time, all trains going in both directions
were passing through out of service.

Could this of been the fault of the ATO system? I would not reckon
that the reason this happened because of adhesion - it was dry and the
conditions were good. I know that the ATO system can 'miss' brake
spots - it happens on the Victoria Line often, that’s why can see the
T/op pulling the red Westinghouse straight-air brake handle on the
offside to adjust the stopping position of the train.

Until now, I've never seen an occurrence like this on the DLR network.