This hypothesis seems to be the starting point of this theory:
The problem of “nonradiative” release of nuclear fusion energy
As we have already noted, the virtual absence of conventional nuclear decay products of the compound nucleus was widely regarded as one of the paradoxes of DD fusion with the formation of 4He in the experiments [2]. We proposed the explanation of this paradox in [4]. We believe that after penetration through the Coulomb barrier at low energies and the materialization of the two deuterons in a potential well, these deuterons retain their identity for some time. This time defines the frequency of further nuclear reactions.
Until we have a good theory, it does not at all surprise me that experiments seems to be not repeatable.
Even something as the temperatures that a metal is forged in and allowed to cool might be enough to make or break the ability for the reactions to occur.
But I have little doubt now - very little, in fact, - that something is going on.
Pons and Fleischman may not have been the greatest theoretical nuclear physicists, but they were thermodynamic chemists par excellence!