Insulated Rail Joiner

On a piece of track rarely used, there's an insulated rail joiner. It does not look like its needed any longer, perhaps it was back in the DC days. No reason to tear up existing track to get to an insulated joiner that's not bothering anything, in fact, I often advocate installing more insulated joiners than you need and wiring around them.

But here's the thing: the rail joiner has melted. It looks like someone tried to attach a feeder to the rails at that point and solder to a plastic rail joiner!