AFAICT this bug was fixed in commit 0b71c15c8 in October 2016:

```
commit 0b71c15c8086544236d3348caedeff3a84ab2948
Author: Eric Bavier <bavier@member.fsf.org>
Date:   Mon Oct 17 17:17:50 2016 -0500

    gnu: slim: Do not reset session after failed login.

    * gnu/packages/patches/slim-reset.patch: New patch.
    * gnu/local.mk (dist_patch_DATA): Add it.
    * gnu/packages/display-managers.scm (slim)[source]: Use it.
```

`~Eric