Suggestions on repairing contact leads

I have a calculator that has a keypad built on the flap that opens. Half of the keys work the other half do not. I have taken it apart and found that the assembly is made of a plastic sheet and copper foil wires/paths that run on top which leads to all the buttons. The plastic sheet connects to the calculator like the spine of a book.

Tested all the channels and found the ones not working. Root of the problem is the opening and closing of the flap has weakened the copper paths at the pivot point.

The paths are black on top and register resistance. The backside of the plastic sheet, the paths are copper.

I have tried using copper foil used to repair PCB's but can not get the proper contact.

Can't solder because it would melt the plastic.

Thought about liquid silver/metal but have never used the stuff and don't know if it will remain flexible after it drys.

Looking for suggestions or products that can repair the damaged paths.

Could u provide a picture?

Here are some pictures

One company that makes just what you need:

https://www.emsdiasum.com/microscopy/products/sem/colloidal.aspx?mm=11

They have a Canadian rep, so maybe it would be easier to get from them, that is if they sell to individuals, and not just a business.