Is there any reason to avoid the Oyster card and buy paper tickets instead?
Most prepay / pay as you go users get the odd incomplete journey now and then, but if you continue to have trouble with pay as you go on your Oyster card I suppose you may as well avoid it. With a season ticket (weekly Bus & Tram pass or Travel card) there is every reason to embrace it. It is fast, smart and flawless. Make a cost comparison here.