Yes, surface and inter-strand corrosion, relaxed contacts over time. I have chased connections on 12v systems where it was less than a volt off. 11 volts acts like 12 volts everywhere else, but not to the ecm on an outboard engine and some other sensitive systems. Even acidic pollution in the air can result in a battery with regard to dissimilar metals, regardless of how noble the metals may be. Half of why they dope sensitive connections with lithium in corrosive environments. Coax the same, and likely worse outdoors if they don't use weather tight connections. The old wire I have here that's tarnished, almost feels like it has a waxy residue on it. It looks brown, but if you wipe it with a paper towel, it comes off green. If it's not shiny copper, it's fouled. The only saving grace may be a secure connection when the wire was new will buy time, but eventually there is bound to be some losses.
Even solder joints get tired over time which is why they may re-flow connections on older equipment, even though they still have a good mechanical bond.