To expand on this... Virtually everything heavier than iron must be formed by stellar explosions.

Either the star explodes, or two stars collide and explode (like neutron dwarf star collisions (NS-NS) )

Iron uses more energy to fuse than it makes in fusion. So, once a star starts to make iron, it is already dying. Supernova only make a small fraction of stuff heavier than iron (5%) the rest is NS-NS collisions.

Well... They have been hoping they would stumble across her corpse eventually... So they probably sang it to themselves to sleep at night.

It seems, (from the comments I have read,) that you already have a working knowledge of the likeliest of problems.

Calling an electrician is certainly the best option.

To continue DIY, you have to make sure you get the proper test equipment and gain at least a basic familiarity of what the readouts say.

Based on your description of the problem, the most frequently suggested problem of a loose connection is very likely the issue.

When a connection weakens, the volts have to increase to cover for that loss. If the amps don't break a breaker/fuse and the amps don't go over the total load and it never faults to gound, you can have issues where lights dim and circuits act funny but not in a way you would expect a failure as a homeowner (grew up with an electrical engineer as a father in a house he owned)

You very likely have a weak connection in a part of the circuit that is rarely serviced. Loose nut, or something similar.

To solve it without test equipment... Shut off all power to the house and check everything. Tighten everything down a smidge and turn it on again to see if it changes.

I would bet several nuts aren't as tight as others and are causing the issue.