Can anyone spot the (very) glaring error in this picture?

What are you talking about?

Does it have to do with the angle that Sayaka is holding the umbrella's handle?

he might be talking about the disappearing umbrella shaft

...Wait. FJH was right. The umbrella's perspective is off. We should be seeing the underside of the umbrella from the angle Sayaka's holding that thing, not the top.

I'll chalk the "disappearing shaft" to being artistic license to keep the shaft from interfering with the art.

that's more like bad art than a straight-out error though :\