Default `member` works fine:

$ guile
> (member 'a '(b))
$1 = #f

However, using scheme base it returns empty list

$ guile --r7rs
> (import (scheme base))
> (member 'a '(b))
$1 = ()

Other functions (memq, memv) seem to work fine.
I am using version 3.0.5 as distributed by debian bullseye