if you don't class weak attempts at saves as errors, then I'm not sure where to start. If a goalkeeper can't save simple shots then that's an error. He's made loads of them.
When I'm not in work I'll come back to this one, but I don't think I said 'leading to goals' specifically, that's your additional caveat.
I think at one point in his first year he had maybe the 3rd worst shot to save ratio int he league. So depends if you want to get into semantics about what classes as an "error".
I'd say the majority of his attempted saves were shit and cost us a lot of points.
But maybe that's just me