  The $\beta$ intensity distributions of the decays of
$^{100\text{gs},100\text{m}}$Nb and $^{102\text{gs},102\text{m}}$Nb have been
determined using the Total Absorption $\gamma$-Ray Spectroscopy technique. The
JYFLTRAP double Penning trap system was employed to disentangle the isomeric
states involved, lying very close in energy, in a campaign of challenging
measurements performed with the Decay Total Absorption $\gamma$-ray
Spectrometer at the Ion Guide Isotope Separator On-Line facility in
Jyv\"askyl\"a. The low-spin isomeric state of each niobium case was populated
through the decay of the zirconium parent, that was treated as a contaminant.
We have applied a method to extract this contamination, and additionally we
have obtained $\beta$ intensity distributions for these zirconium decays. The
$\beta$-strength distributions evaluated with these results were compared with
calculations in quasiparticle random-phase approximation, suggesting a prolate
configuration for the ground states of $^{100,102}$Zr. The footprint of the
Pandemonium effect was found when comparing our results for the analyses of the
niobium isotopes with previous decay data. The $\beta$-intensities of the decay
of $^{102\text{m}}$Nb were obtained for the first time. A careful evaluation of
the uncertainties was carried out, and the consistency of our results was
validated taking advantage of the segmentation of our spectrometer. The final
results were used as input in reactor summation calculations. A large impact on
antineutrino spectrum calculations was already reported and here we detail the
significant impact on decay heat calculations.
