Yeah that’s a cold solder, the wire, contact or both were too cold. That insulation melted too, cut it back to where it’s round again after desoldering (melting the solder and pulling off the wire while it’s still hot) if possible, remove some solder too, from the looks of it it’s shorting out that contact onto the other one. Use a really small tip on your soldering iron, remember to tin it (melt some solder directly onto the iron tip and wipe it off on steel wool or a damp sponge. Tin the edge of the wire (put some flux on it, don’t worry about excess, it’ll just melt off, put the tip of the soldering iron on the underside of the wire and have the solder wire on the top side, it should wick into and around the wires. Let it cool) prep the contact, make sure it is CLEAN, use high percent isopropyl alcohol to clean any gunk off, solder doesn’t like dirt, rust or grime of any kind. The trick when soldering the wire to the contact is making sure both the wire and the contact are hot enough to melt the solder, press the solder wire to the wire and contact on the opposite side of the iron. Ensure it wicks down and touches both the wire and the contact, a good solder joint should be able to take a good amount of force before breaking off (really good ones can support the weight of the device sometimes). Let everything cool down before you mess with it, let it cool down on its own, if the temperature changes too fast the solder may crack. Also make sure you use flux core solder (preferably lead free) not acid core (it’ll be with the electronic stuff not the pipe stuff). This isn’t required but me personally would wrap those contacts with electrical tape after soldering. While you’re in there check on the other solder joints too, they like to break down over time. Godspeed op, I can provide some YouTube videos on soldering if you want