Upgrade impossible de 4.501B à 4.503 B sur de nombreuses HCL ( message Error - invalid checksum )   => faire une sauvegarde  en 4.501B source fibaro   ou can try to install new version manually:
1) Put your HCL in a recovery. Here is a video tutorial:
Home Center Lite https://www.youtube.com/watch?v=IMD4kKaIV_o The procedure is:
a) Turn off the device by disconnecting power supply.
When turned off, turn it on again with recovery button “+” pressed (next to power button).
c) When LED are flashing from left to right, please release recovery button “+”.
d) Now open recovery mode in your web browser.
e) From menu please choose second option- “Load file” and use “Choose file” button.
f) Now as file to load please use patch file available to download here: http://updatehcl.fibaro.com/4.503/patch.tar.gz
g) After above step installation of new software should start
h) After correct installation, your HCL should restart and turn on in new version 4.503 => faire une restauration ……..