I had that code reader too, I think it’s just a feature* of it that it brings up a brake error when you interrogate the parking brake module.
Any issue with the parking brake will be related to the NS parking brake motor which is a really cheap nasty pattern part which didn’t fit very well.
Decided I’m never going to get around to fixing the Astra so it’s on eBay.
Attracting more interest than I expected tbh
https://www.ebay.co.uk/itm/156108780004?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=UtJpyBAgQKy&sssrc=4429486&ssuid=UtJpyBAgQKy&var=&widget_ver=artemis&media=COPY