Welcome fellow biker. Indeed, disconnection of battery in the wrong manner, as I did too, will bring up a handbrake fault.
Not saying this will cure it, but worth a try. Shut doors & remote lock, leaving drivers window & bonnet open.
Leave for 5 mins (to ensure Computer has gone to sleep).
Disconnect battery, Wait 5 mins, Reconnect, Again wait 5 mins, DO NOT open doors or touch anything during the wait, Turn on side lights through window (no I don't know why either), then use car as normal.
You will need to reset the windows & have a radio code. Seems fluctuating voltages upset the
. Do a search, there are threads where similar procedures have achieved a handbrake reset. I had to do mine the hard way, with code reading software.
Do you have any dashboard nags flashing up?