When preparing artwork for books, it is normal practice to allow bleed on the top, bottom, and foredge of a page, but not the spine, as the bleed would show up on the facing page.

However, when preparing artwork for books where the pages are essentially loose leaves held together without the use of glue or staples (e.g. comb, wire-o, ring, coil etc), bleed does in fact have to be applied to the spine.
This is not a problem if the bleed from one page to the other is consistent, but if the art abruptly stops from one page to another, then this will present a problem as the bleed will now appear on the opposite page.
On the outset, this problem looks like it cannot be overcome easily, but there is a way to do this:
1) from the pages flyout, uncheck the tick “Allow document pages to shuffle”
2) go to the affected spread in the pages palette and click and drag the right hand page to the right hand side until the icon turns into a hand holding a blank piece of paper with a black line to the right hand side of the page being moved
This will result in the spread being split in two.

From here, pull the bleeds out on the spines as required.

This is fine if correcting one spread, but for correcting an entire book, a script may be a better solution. it can be found here. Just make sure that the file is saved before doing this as I have noticed some issues with using this script.
This is also something which should be done once the page count and order is finalised, as swapping pages around after turning off “allow document pages to shuffle” can be complicated.