BIR: Inconsistent behavior derived from cando

[Bike]

Compiling and loading this file, and then calling (builder-test::add-relations :cando (cons nil nil) `((* :element (,(core:make-cxx-object 'chem:atom-test :sym :C :test :sapelement) ,(chem:make-bond-to-atom-test :sabany-bond nil))))), sometimes results in a problem where relate is not called when it ought to be. Further reduction to come. 2Crh.txt