gc shows some roots more than once and others are skipped

[BP25]

Hello! Does anyone know why guix gc --list-roots displays the same files 
more than once in some cases (for instance current-guix2-link appears 
three times) and some never (current-guix) does not appear. Note that 
everything seems in order when I list such files with the ls command: 
all the ones which should appear do show up, and only once.