Is the 9v jack pin long enough? Sometimes - especially with daisy chains - you need to strip some of the rubber round the pin so it will seat into the socket properly. I've had to do this with Joyo pedals, not sure about Behringer though.
Also my first bass bought in the mid noughties. Electrics were foofed and the bass was proper manky. I took it all apart to clean and ended up losing half the parts 😂 ah well.
Hey Dude, welcome!
I am also from the North East, Aberdeenshire. Hope you have plenty bawbees in your wallet as you'll need it here if you venture into the marketplace! 😂😂😂