  Solar Orbiter's four in-situ instruments have recorded numerous energetic
electron events at heliocentric distances between 0.5 and 1au. We analyse
energetic electron fluxes, spectra, pitch angle distributions, associated
Langmuir waves, and type III solar radio bursts for 3 events to understand what
causes modifications in the electron flux and identify the origin and
characteristics of features observed in the electron spectrum. We investigate
what electron beam properties and solar wind conditions are associated with
Langmuir wave growth and spectral breaks in the electron peak flux as a
function of energy. We observe velocity dispersion and quasilinear relaxation
in the electron flux caused by the resonant wave-particle interactions in the
deca-keV range, at the energies at which we observe breaks in the electron
spectrum, co-temporal with the local generation of Langmuir waves. We show, via
the evolution of the electron flux at the time of the event, that these
interactions are responsible for the spectral signatures observed around 10 and
50keV, confirming the results of simulations by Kontar & Reid (2009). These
signatures are independent of pitch angle scattering. Our findings highlight
the importance of using overlapping FOVs when working with data from different
sensors. In this work, we exploit observations from all in-situ instruments to
address, for the first time, how the energetic electron flux is modified by the
beam-plasma interactions, and results into specific features to appear in the
local spectrum. Our results, corroborated with numerical simulations, can be
extended to a wider range of heliocentric distances.
