MIG wrote:

Well, in the OEP staff briefing it says, in one place

"Once the OEP is loaded, when the customer touches-in to start a
journey even if it is within a Zone covered by their Season ticket, an
entry charge will be deducted from the card.
If they touch-out still within the Zonal coverage of their Season
ticket, the entry charge will be refunded and the OEP will remain on
the card. If they touch-out in another Zone the fare for the
additional travel will be deducted from the entry charge, the PAYG
balance will be adjusted accordingly and the OEP will be cancelled."

Okay the nightmare station for Oyster - Wimbledon. What if you have a stored
OEP but enter the barriers to use the tram?