Have a look at this thread Zivan NG1 heating input 120VAC pigtail
I talk about a design flaw which can also cause problems including help melt the fuse holder.
In the pictures I posted you can see the burned spade connectors for the 120VAC input power but also look behind those and you’ll see the tall black fuse holder(screw driver slot on top ).
Possible failures on this corner of the power supply for sure.
I hadn’t posted pictures but one of the things I did after the fact was to drill some air holes in the plastic case around these components to help keep them cool.