I work on this gear every week. First off, the ferrule is not seated in the barrel adjuster. This has to be fixed, perhaps this setup doesn't need a ferrule. This configuration may cause the cable to be rubbing against the metal edges of either the ferrule or the adjuster, eventually causing it to fail/snap. Then: no braking at all.

Second, it looks like the cable tie was installed to prevent the caliper quick-release from falling off the brake. Not good: suggest replace the entire quick release/adjuster.

Nevertheless: the bottom line is that these Dia-Compe brakes from the 70's feature poor mechanical advantage, cheap hardware and weak flexy arms. They were a blight on the bike industry for decades, and with hardened 40-year old pads, they haven't gotten better at braking. We strip these off of bikes at every opportunity and deep-six them into recycling. Brakes are critical to your safety - get rid of these and invest in something better.