I've been away from London for several months, but on my return (and
after Oyster had gone live) I've noticed that irritatingly my
(traditional card / mag stripe) annual gold card now prompts an error at
all the underground gates I've gone through - both entrance and exit
gates - which means delay, and having to ask to be let through a gate by
an operative waiving their Oyster card. Yet at main line rail terminals
London Charing Cross and London Bridge there's been no problems at all
with the gates.

Is this an unintended consequence of Oyster? Or is something else the
cause? Anyone else experiencing the same enhanced service?

The gold card runs 'til next May, so I guess that's when I'll get an
Oyster card ..... but having to put up with this hassle for another 5 or
so months is a pain.