lsb_release / base-files in Debian unstable changed its output data, and thus facter reports different values. Because they contain a "/", facts upload fail with this error:

During the fact upload the server responded with: 500 Internal Server Error. Error is ignored and the execution continues.
{
 "error": {"message":"Validation failed: Major version is not a number, Major version Operating System version is required"}
}

facter output (from puppet-agent 7.21.0-1bullseye deb):

os => {
  architecture => "amd64",
  distro => {
    codename => "bookworm",
    description => "Debian GNU/Linux bookworm/sid",
    id => "Debian",
    release => {
      full => "bookworm/sid",
      major => "bookworm/sid" 
    }
  },
  family => "Debian",
  hardware => "x86_64",
  name => "Debian",
  release => {
    full => "bookworm/sid",
    major => "bookworm/sid" 
  },
  selinux => {
    enabled => false
  }
}

$ /opt/puppetlabs/bin/facter --version
4.2.14

$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux bookworm/sid
Release:        n/a
Codename:       bookworm

Debian bug about the change: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1021663