> `switch-to-buffer-other-window' no longer uses the "other" window.
 >
 > Using a new emacs via "emacs -Q":
 > `C-h i' - Displays the *info* buffer
 > `C-x 4 b RET' - Displays the *scratch* buffer in a second window
 > `C-x 4 b RET' - Fails to replace the *info* buffer with the *Messages*
 >                 buffer.  Replaces the *scratch* buffer instead.

Thank you very much for the report.  Can you please try whether the
attached patch fixes it?  It incorporates a number of changes unrelated
to the bug you found.  The change needed to fix the bug you found is the
last one in the patch on lines 1011-1018.