Ibooks Issue, reading from a given page does not always work

Hello there.
I would rather use iBooks on Mac, because there are more voices available than on an iPhone, especially if you are lucky enough to have an Intel Mac, which allows you to use a cappella voices for a while more.
But on the Mac, when selecting a page to read from, the book often, but not always starts from its beginning. Furthermore, I cannot get the Mac to read the whole book at once, it will always stop at a point, which is not necessarily the end of the current page.
I'm on big Sur.
Any advice?
Thanks,
JPR