Lehner 1930 De-soldered Itself??

I had no idea that changing the configuration on a Lehner was so easy. The thing about your problem is that if the traces got hot enough to melt the bridges that you soldered, there would have been some residual heat there when you checked it.

What about using some small strips of copper to bridge the connections rather than just bridging them with solder? It might be better, but on the downside, if that strip desolders and slides, there's no telling where it might end up, and that could be bad. Very bad. LOL