  We present a hypothesis that the anomaly in the folding angle distribution of
electron-positron pairs, emitted in the decay of the excited levels of nucleus
$^{8}$Be and $^{4}$He can be related to the cluster structure of the decaying
state. Furthermore, we present a hypothesis that the potentially observed boson
with re st mass $m_{X}$=17 MeV can mediate the nucleon-nucleon interaction at
the low-energy regime of QCD, in particular in the weakly bound cluster state
p+$^{7}$Li,$^{3}$H. We present a possible equations of state of symmetric
nuclear matter corresponding to the vector meson mass $m_{v}$=17 MeV, obtained
using relativistic mean field theory of nuclear force, QHD-I in particular,
with physically relevant incompessibility K$_{0}$=240-260 MeV and the values of
couplings $g_{v}$, $g_{s}$ lower than unity. Based on concepts of chiral
symmetry breaking, we show that reduction of the rest mass of pseudoscalar
particle from physical value $m_{\pi}$=135 MeV to $m_{X}$=17 MeV is equivalent
to reduction of the quark mass from dynamical value around 310 MeV down to
current quark mass around 5 MeV ($\frac{m_{X}^2} {m_{q,curr}} \simeq
\frac{m_{\pi}^2} {m_{q,dyn}}$). Corresponding version of Goldberger-Treiman
relation leads to the value of coupling close to the results from relativistic
mean field theory of nuclear force. Both model approaches thus point towards
apparent restoration of chiral symmetry in nucleon-nucleon interaction at large
distances, possibly via bounce into false instanton vacuum. Observation of
boson with rest mass $m_{X}$=17 MeV in the decay of high lying excited states
of $^{8}$Be and $^{4}$He can possibly resolve one of the longest lasting open
questions in nuclear physics.
