Testing something before installation and long-term reliability are two different things. In many cases, there's no way to accurately test/predict how something will operate years down the road. Especially in an indoor environment that has a lot of water flowing through it. They just did the best they could, and it is what it is.
As for it happening or not happening from one day to the next (or sometimes even one ride to the next), sometimes the logs are too close together for Rabbit to hop for every log. He can't reset fast enough before the next log trips the sensor.
The last time I went, it appeared that they had removed the "hedge" that he hops along that hides his support arm. You could see the support arm behind him quite clearly. Perhaps the hedge was one of the reasons for his frequent downtime, as the arm has to reach the far end of the hedge before it can rotate him around, down and back to start. If he were to turn too early, he'd crash into the hedge. He's easily the most complex AA figure in the attraction. And while I doubt the figure *cost* $1-million, with all the continued maintenance that goes into him, it's always possible that they've spent a million over the years keeping him running...err, hopping...
(Or perhaps to the maintenance budget people it just *seems* like a million)
-Rob