  We investigate the migration of Mars- to super-Earth-sized planets in the
vicinity of a pressure bump in a 3D radiative protoplanetary disc while
accounting for the effect of accretion heat release. Pressure bumps have often
been assumed to act as efficient migration traps, but we show that the
situation changes when the thermal forces are taken into account. Our
simulations reveal that for planetary masses $\lesssim$$2\,M_{\oplus}$, once
their luminosity exceeds the critical value predicted by linear theory, thermal
driving causes their orbits to become eccentric, quenching the positive
corotation torque responsible for the migration trap. As a result, planets
continue migrating inwards past the pressure bump. Additionally, we find that
planets that remain circular and evolve in the super-Keplerian region of the
bump exhibit a reversed asymmetry of their thermal lobes, with the heating
torque having an opposite (negative) sign compared to the standard circular
case, thus leading to inward migration as well. We also demonstrate that the
super-critical luminosities of planets in question can be reached through the
accretion of pebbles accumulating in the bump. Our findings have implications
for planet formation scenarios that rely on the existence of migration traps at
pressure bumps, as the bumps may repeatedly spawn inward-migrating low-mass
embryos rather than harbouring newborn planets until they become massive.
