Melted Heatbed Terminal
Hi, last time I went to print my heatbed wasn't heating up at all, so I opened up the board and undid the screws to find this. Everything seemed to be connected correctly so I'm not sure which parts I should replace or what to do differently.
RE: Melted Heatbed Terminal
It looks like you had a bad crimp on the spade lug to wire connection. It over heated and melted everything. It looks repairable.
Replace the lugs on both wires in that photo. When stripping the insulation back, make sure you strip back to clean copper. Then crimp on new spade lugs, but find a good crimp tool. Or solder the lugs on. Adding a dab of dielectric grease on the wire before crimping won't help a lot, but might not hurt if all you have is a typical Harbor Freight crimp tool.
There are small fiberglass brushes available; use one for cleaning off the terminal on the circuit board. A small brass or steel wire brush will work, but watch for loose bristles springing off and lodging on the circuit board.
Check the solderside of the circuit board - make sure the terminal strip pins are still glossy. If any are matte or spongy looking, especially the ones that got hot, re-tin them so the solder is shiny.
And as a last step, install the lugs, tighten the screws down tight, but do it only once. Then, go back to all the other screws, loosen them, then tighten them back down. Somewhere I read tightening a tight screw causes longer term problems; maybe that was circuit breakers and solid wire, but I try to follow the hint and - so far - it's never been an issue.
RE: Melted Heatbed Terminal
As a post script, you may have other issues, like a bad connection on the heat bed side, too. So pop off the wire cover and check the heat bed still looks okay. Any sign of hot wires or connections needs attention.