Fuel Door Release Cable

[Drum]

Hello all. I have a Toyota Yaris 2014 (2012-2014 5-door hatchback). I had problems with my fuel door release cable (I think) last winter when I could not lift up the lever to open it. If I did manage to lift it and open the flap, it would stay up, and the pin would remain compressed. Then it would slowly release itself. This only happened at below-freezing temperatures (I am in Canada), and when it melted, everything was fine. We are in the summer now, and it was +30 and raining the other day. I pulled up to a gas station and had the same problem. The lever by the passenger side was tight; I did open the flap, and the pin remained compressed for a while. After doing some research, it might be some rust on the cable preventing it to slide freely. Lubricating the pin from the outside is useless, nothing gets onto the cable itself. Is there any way to pull it out slightly outside to try to spray the lubricant onto the cable and not the plastic parts? I have a photo of what it looks like from the inside (taken from the access to the tail light, and I can only feel it with my fingers, going inside there with a tool would be close to impossible since the space is really restricted). If this could be pulled in or out, I could then try to spray the lubricant with a thin nozzle inside and see if it solves the problem.

I am also considering replacing the release cable altogether, but how difficult is it? Would I have to remove the seats for that?