On the brake cartridge, have you got the thin spacer on the rim side or the outside of the brake arm ?.
Thin ones, chunky ones mean there's not enough spring power.
If the spring tensioner screws are adjusted correctly they should have more than enough power, so it could be the pivots are sticky.
Can send you flexible noodle foc to try or you can use a car type brake pipe bender to alter a fixed noodle to any angle needed.
That's very kind but I have one already, if I whack up the spring tension the noodle may sit straighter in the carrier bit which may help.