fish glue?! WTF?

Bakelite is made from fish bones and when it starts over-heating it smells vaguely fishy. Overheating is usually from contacts/joints that are going high resistance. A bit of heat causes copper to expand, and the deformation from screws in the joint, which contract when cold. This then causes a bit more resistance which causes more heating. A vicious cycle then takes place which may take years but if the fuse or junction box is Bakelite ... it starts to cook. And smell. Not many of those installations left but I have experienced 4 fish smells in the last 25 years and they were all Bakelite, solved by replacing with modern hard plastic.

As to the liquid, it is most likely something that got inside sometime in the past. And a brew is implicated. Could be tea, how likely is that?