One cantilever arm will not release fully

[Futs]

I'm super new to bike assembly/repair and I'm currently working off of just internet guides and YouTube tutorials to fix this bike I found in a dumpster.
Long story short, I took it apart and painted it and now I'm trying to put it back together but have hit a couple snags. My most current one being that on the rear brakes only one of the cantilever arms will actually release after I let go of the brake lever. The one arm that is giving me trouble is the one connected via the link wire or button (I think that's what it's called).

[FredS]

Take the brake arm off and check if the spring is broken, if not check that it is in the same hole that the other one is in and readjust.

[1FJEF]

Yep, it's normally the center hole. Check BOTH arms.