Had this issue for over a year and I've been to the dealer who looked at it and said I needed to replace the entire hardware in the rear wheel, which was way overkill because it includes the brakes and all. They wanted something like $800 for it! They even agreed it's way overpriced but nothing they could do on price...
I've just not been using the parking brake at all. If I try and push the brake handle down from the driver's seat, it pops back up on me because it won't release. I've tried WD-40 on the brake's spring in the rear wheel and didn't help, figuring it was getting stuck. I'm pretty sure all I need is that spring as it's not enough spring in it to release the mechanism, but not entirely sure. I've played with it countless times and only way I can get it to release is to hit the release with something so it disengages.
If I loosen the nut back there, it just loses tension and doesn't help. I have no experience with parking brakes but it's not all that complicated. Just would like to have a brake and not worry about parking on a hill and the gear becoming disengaged from someone when I'm not there.
Unsure what I could except maybe posting if anyone has a junked sling that would sell me that spring.
See pic for what I mean. It's not mine, just an image I found.