I added the "/T" option to taskkill. Otherwise if e.g. an epub reader instance is in use the calibre-parallel.exe process blocks the update.
@PeterT
Did you try these options. In my case none of the CLI options had any effect.
@jemkeith
Yes I have done it the same way, here some (hopefully useful) hints for scheduling configs:
trigger: weekly at night before boot or login
action: start program: cmd
arguments: /c start /min "" <path-to-bat>/UpdateCalibre.bat
condition: connection available
config: start if missed
You could also add "--no-update-check" to your calibre link but I am not shure if it really works.