Yeah I didn't notice that feedback from this discriminator, which in any case I don't understand how it works.
The waveform shown in the schematics looks shaped to me. Whatever is doing this shaping deserves investigation.
I'd dump the whole circuit into LTSPCE with careful evaluation of paramaters and simulate away!
Carbon comp resistors need to be checked for drift. They can go out by 20% or more after so many decades.
