Is there something wrong with the book search feature or is it book specific?

Is there something wrong with the book search feature or is it book specific? I was recently searching within some books on my iPhone and noticed it took me to the wrong location, such as the start of the previous chapter. I’d for instance see 5 results for the same searched word and they’d all say page 99. I however noticed it seemed to work fine on my iPad so I’d use that instead until today when those books updated on my iPad as now the search feature also seems broken on there. As it happened after an update it seems related to that.