  Appearance of quantum oscillations (QO) in both thermodynamic and transport
properties of metals at low temperatures is the most striking experimental
consequence of the existence of a Fermi surface (FS). The frequency of these
oscillations and the temperature dependence of their amplitude provides
essential information about the FS topology and fermionic quasiparticle
properties. Here, we report the observation of an anomalous suppression of the
QO amplitude seen in resistivity (Shubnikov de-Haas effect) at sub-kelvin
temperatures in ZrTe5 samples with a single small FS sheet comprising less than
5% of the first Brillouin zone. By comparing these results with measurements of
the magneto-acoustic QO and the recovery of the usual Lifshitz-Kosevich
behavior of the Shubnikov de-Haas (SdH) effect in ZrTe$_5$ samples with a
multi-sheet FS, we show that the suppression of the SdH effect originates from
a decoupling of the electron liquid from the lattice. On crossing the so-called
Bloch-Gr\"uneisen temperature, T$_BG$, electron-phonon scattering becomes
strongly suppressed and in the absence of Umklapp scattering the electronic
liquid regains Galilean invariance. In addition, we show, using a combination
of zero-field electrical conductivity and ultrasonic-absorption measurements,
that entering this regime leads to an abrupt increase of electronic viscosity.
