This problem is solved. I can't reproduce it with
$ guix describe
Generation 64 Mar 20 2020 13:54:14 (current)
guix 830dab8
repository URL: https://git.savannah.gnu.org/git/guix.git
branch: master
commit: 830dab870ab1d4a4ec1127a877a43d19f86c4f7f$ rhythmbox --version rhythmbox 3.4.3 I couldn't find any commit in the log of Guix's git repository addressing this issue.
