Yes, it is now extremely temperamental. I have a Freedom Pass which is
essentially an Oyster Card. Yesterday I travelled by Central Line from
Leyton To Stratford. No problem at either end. Coming back from Westfield
towards The Broadway, I decided to cut through the station. I used my
Freedom Pass to gain access. Again, no problem. At the other side of the
station, my Pass was not accepted. The member of staff who let me out
of prison agreed it was probably because it was too soon after I had
entered.

I did some shopping and about 30 minutes later tried to enter the station
again. My pass was not recognised. I decided to walk home. (From Stratford
it's not too far, I need the exercise and I was in no hurry) The journey takes
me past Leyton Underground Station. On a whim I decided to check my
Freedom Pass. Accepted without any problem.