After cleaning up my profiles, and some other troubleshooting, I eventually realized that the failure can be bypassed by setting guix-repl-use-server to nil, i.e., disabling emacs-guix from using the additional Internal REPL (#<buffer *Guix\ Internal\ REPL*>).
The Internal REPL gave me trouble in another bug as well. I'll need to try to get a better understanding of how the magic of the Internal REPL works and how it could be messing this up. -- Christopher Howard
