Top bar appears after a few hours in full screen kiosk mode

[abctaylor]

Has anyone seen this behaviour? Initially it starts perfectly:

After some time (typically overnight) the top bar appears:

Pi 5 Bookworm.

config file:

general:
  kiosk-mode: full
  autofit: true
  lxde: true
  lxde-home: /home/l-admin
  scale-factor: 1.0

target:
  login-method: local
  username: xxxxxxxxxxxxxxx
  password: xxxxxxxxxxxxxxx
  playlist: true
  URL: https://grafana.core.example.net/playlists/play/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx?kiosk&autofitpanels