The ball launcher was misbehaving. The outside spring had at some point fractured. I tried fixing it recently, and it was fine for a bit, but it was bad yesterday during the tour. Today I ended up removing one of the chunks, as it was getting tangled in the other and making things less elastic. Works for now, but I should replace it. And since there are problems unscrewing one of the screws, maybe better just to get a new assembly?