I can't offer any advice Mark because, I've got no experience of FWB rifles all.
But, my thought is that you should keep it and persevere with it.
From reading your earlier posts about this rifle and, knowing your reasons for buying it, I know how pleased you'll be when it finally comes on song
It may take a while to sort but, don't get disheartened. When you're pissed off with it, put it away for a while - even it's in the cupboard for weeks.
...... It'll get there in the end and, you'll be glad when it does