In multiple test runs, I'd seen a coredump for /bin/login; I am, at this
moment, not aware of any directly visibly effect on the user - but this basic
system must really not crash

backtrace
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007f662c5fcda1 in __GI_abort () at abort.c:79
#2  0x00007f662946d9f6 in log_assert_failed_realm
(realm=realm@entry=LOG_REALM_SYSTEMD, text=text@entry=0x7f6629474cb0 "fd",
file=file@entry=0x7f662947e317 "../src/basic/socket-util.c", 
    line=line@entry=1011, func=func@entry=0x7f662947e350
<__PRETTY_FUNCTION__.11108> "getpeergroups") at ../src/basic/log.c:820
#3  0x00007f6629472011 in getpeergroups (fd=<optimized out>,
ret=ret@entry=0x55d6c71f1058) at ../src/basic/socket-util.c:1011
#4  0x00007f6629464e07 in bus_get_peercred (b=0x55d6c71f0e40) at
../src/libsystemd/sd-bus/bus-socket.c:623
#5  bus_socket_start_auth (b=b@entry=0x55d6c71f0e40) at
../src/libsystemd/sd-bus/bus-socket.c:674
#6  0x00007f66294652e4 in bus_socket_connect (b=b@entry=0x55d6c71f0e40) at
../src/libsystemd/sd-bus/bus-socket.c:935
#7  0x00007f662945770f in bus_start_address (b=0x55d6c71f0e40) at
../src/libsystemd/sd-bus/sd-bus.c:1120
#8  0x00007f662945a8ca in sd_bus_start (bus=0x55d6c71f0e40) at
../src/libsystemd/sd-bus/sd-bus.c:1204
#9  0x00007f662945abb7 in sd_bus_open_system (ret=ret@entry=0x7fff6eef9120) at
../src/libsystemd/sd-bus/sd-bus.c:1305
#10 0x00007f6629445c68 in pam_sm_close_session (handle=0x55d6c71cf600,
flags=<optimized out>, argc=<optimized out>, argv=<optimized out>) at
../src/login/pam_systemd.c:530
#11 0x00007f662cdb05d4 in _pam_dispatch_aux (use_cached_chain=<optimized out>,
resumed=<optimized out>, h=0x55d6c71e0040, flags=0, pamh=0x55d6c71cf600) at
pam_dispatch.c:110
#12 _pam_dispatch (pamh=0x55d6c71cf600, flags=0, choice=5) at
pam_dispatch.c:426
#13 0x000055d6c614520c in ?? ()
#14 0x00007f662c5e6a87 in __libc_start_main (main=0x55d6c6144400, argc=4,
argv=0x7fff6eefa768, init=<optimized out>, fini=<optimized out>,
rtld_fini=<optimized out>, stack_end=0x7fff6eefa758)
    at ../csu/libc-start.c:308
#15 0x000055d6c614655a in ?? ()