For the text 123 (abc) 456, performing y% or d% yanks / deletes the wrong text. In this example, it selects 123 ( and 123 (abc) when the cursor is on the opening and closing parens, respectively. The expected behavior is to yank / delete (abc) in both cases.

In larger buffers, the beginning of the incorrect selection isn't necessarily the beginning of the buffer. It sometimes starts hundreds of characters before the opening paren.