Have you tried clicking on page 40 and dragging it slightly to the right away from page 39? This should work. If it does do the same with page 39.
Hope it works. If not, let us know.
Wow! That worked so easily. But... for some reason page 38 (the page before the added pages) and page 41, the page (after the added pages) are both set in square brackets in the thumbnails (...  . Does this cause any problems?
Thank you for the prompt and helpful response.
It shouldn't be a problem. Not sure why it's doing it.
Try selecting each page that's in brackets and choose "Allow Selected Spreads to Shuffle" under the Options menu of the Pages panel.
Hope this helps!
That did the trick. You are so kind to answer so promptly.