> When using the calculator function of GNU Emacs 31.0.50 (bug also found
 > in 29.4), usage of `calculator-electric-mode' causes Emacs to hang on
 > subsequent uses of the minibuffer.
 >
 > Emacs -Q
 >
 > M-: (setf calculator-electric-mode t) <RET>
 >
 > M-x calcu <RET> q M-x M-p <RET>
 >
 > Note that the freeze does not depend on specifically calling calculator
 > a second time, and calculator may be repeated with C-x z without issue.
 >
 > The freeze occurs specifically when the minibuffer exits a second time,
 > even via C-g, before its contents are processed. Thus, for example, the
 > following still yields a freeze:
 >
 > Emacs -Q
 >
 > M-: (setf calculator-electric-mode t) <RET>
 >
 > M-x d-o-e <RET> kill-emacs <RET>
 >
 > M-x calcu <RET> q M-x kill-emacs <RET>
 >
 > Apparently, calculator-electric-mode leaves the minibuffer window in a
 > broken state after first usage, rather than resetting it correctly.
 >
 > Emacs must be killed externally at this point, and generally cannot be
 > salvaged with C-g. It becomes trapped in a loop emitting terminal bells
 > (seen with `visible-bell' mode on, or via a termscript from `-nw').

This bug is a consequence of accessing the list of previous buffers for
a minibuffer window.  That list is conceptually unmaintained and
therefore unsafe for minibuffer windows.  In particular, 'kill-buffer'
and subsequently 'replace-buffer-in-windows' do not consider minibuffer
windows.  The doc-string for the latter now states explicitly that
"Minibuffer windows are not considered."  Handling minibuffer windows in
'replace-buffer-in-windows' might require some deep surgery and is
certainly not recommended for a release branch.

I can offer the attached patch to provisionally handle this problem.

martin