bm-1.43.el visual bookmarks broken

[Maindoor]

This is a neat bookmarking tool. But it is broken.
http://download.savannah.gnu.org/releases/bm/bm-1.43.el

The broken version is still there in emacs-goodies.
Raising a bug gets nowhere.
To recreate set 3 boomarks across buffers and do bm-next and 
bm-previous on it. That should highlight the problem. 
bm-next just alternates between two bookmarks. bm-previous works fine.
bm-next does not cycle through all the buffers. 
also do a (setq bm-cycle-all-buffers t)

How can I debug this issue ? doing a debugger and 
single stepping ( d ) taken me into an infinite loop.
This is my first hand at looking at lisp code.

Any suggestions ?

-Maindoor