Restoring old m-track h0 layout, have a 5207 crossover where the wire “pin” that flips the track is broken. I tried soldering a paper clip here which works, but is to stiff if there is traffic coming over way needs to have some spring to it.

Any suggestions for how to repair? (I don’t think Marklin even sold a replacement part here except for the whole double arms?)

Picture of needed part replacement :

It needs 0.5mm (I think, or even 0.3mm) spring steel wire ("Federstahldraht") that cannot be soldered. They crimped it. If you succeed to open it, you can try to recrimp the new wire, else glue it in with 2 component epoxy resin.