I have an annual travelcard on my Oyster. I travelled to North Sheen, touched out on the validator then, after 1-2 minutes, tried to touch in again, on the same validator, to make the reverse journey, but it wouldn’t let me, saying “this card has already been used” (the short time at NSH was because I was accompanying someone home part of the way before returning home; I couldn’t delay the touch-in any longer as the train was arriving).
Looking back at my Oyster statements for similar trips, I’ve successfully touched back in at Kew Bridge and Chiswick within three minutes of touching out- is this because I used a different validator on a different platform? Or is three minutes the minimum time for exit/entry?
If I hadn’t touched out or in at NSH, would I have had problems exiting the gates back at my home station? Your info page on same station exits refers to PAYG rather than travelcards I understand.
You need to wait 2 minutes at validators unless continuation exit is set, when it’s then 15 minutes.
What effect it would have depends on whether North Sheen is covered by your travelcard or not. If it is then it won’t be a problem. If not then you’ll technically have an unvalidated card until you get into your zones. This would only be an issue if you are checked by an inspector.