> As a temporary workaround you can try to set the buffer local values
 > of 'scroll-bar-width' to zero in all buffers that might eventually
 > show up in the minibuffer window, for example, thusly
 >
 > (progn
 >    (set-window-scroll-bars (minibuffer-window) 0 nil)
 >    (with-current-buffer (get-buffer-create " *Echo Area 0*")
 >      (setq scroll-bar-width 0))
 >    (with-current-buffer (get-buffer-create " *Echo Area 1*")
 >      (setq scroll-bar-width 0))
 >    (with-current-buffer (get-buffer-create " *Minibuf-0*")
 >      (setq scroll-bar-width 0))
 >    (with-current-buffer (get-buffer-create " *Minibuf-1*")
 >      (setq scroll-bar-width 0)))
 >
 > This should work as long as you don't enable recursive minibuffers.

Have you ever tried that workaround?

I now attach a patch that should address this problem with the help of
an additional argument PERSISTENT for 'set-window-scroll-bars' and
'set-window-fringes'.  If set, the requested settings should survive
subsequent invocations of 'set-window-buffer' for the window (in
particular the minibuffer window) in question.  If you build Emacs
yourself, please try it.

Thanks, martin