"... his original version worked fine and was stable. The experience of breaking refers to later versions that were expanded by his doctoral students and others

"... his original version worked fine and was stable. The experience of breaking refers to later versions that were expanded by his doctoral students and others and to ports to java and I think C." I can believe this but I think your details overall reinforce my points above. For a recursive descent algorithm it had some clever means of jumping to anticipated alternative analyses rather than doing a standard backup. Yeah, fabulous but extremely hard to extend or reproduce. The aim of companies was to scale something like this. It seems like the fundamental problem was only a few really smart people could programs to this level and no one could take them beyond it (the saw that a person half to be twice as smart to debug a program as to write comes in, etc).