Slightly different issue here...

Last night I hopped onto the DLR at WIQ on the way home, part way of which
Id have to use the Central Line.

I was half expecting to use the standalone Oyster validators on the
Westbound platform at Stratford to simulate an "entry" on my Oystercard - I
was afraid that I wouldnt be allowed out at my destination station if I
didnt (since I had read that you NEED to use the Oyster on entry AND exit,
regardless of whether the gates were open).

The validators at Stratford didnt work - they seemed to be switched off. The
gates at my destination were open anyway, but on scanning my Oyster they
gave me green (so I assume Id be able to get out if they were shut anyway).

Do Travelcard Oysters need to be scanned on exit and entry?