Magic Keyboard - iPad - Kindle iOS Reader -flipping pages

I have used Magic Keyboard with my iPad 7th gen while on the treadmill, to flip pages in ebooks and Kindle books. This worked perfectly until 2-3 weeks ago, when page flipping and "returning to desktop" stopped working with my Kindle Reader, even as other controls (brightness, sound volume) kept on working. Nevertheles, when reading ebooks bought from Apple, all keyboard shortcuts went on working as before. And the keyboard otherwise works for typing and other general stuff in my iPad.

Since only Kindle books are affected, could this result from some change in Kindle software or is it a keyboard malfunction? If somebody has a clue, please let me know whether I should buy a new keyboard and all will be fine or whether from now on, I should forget about reading on the tradmill and downloading any more Kindle books.