Conservation of mass is a synthetic a priori judgement (Kant). If mass is not conserved, mass values are false.

There is no mass defect, Einstein misled physics. Kant is right.
To identify energy and mass is a category mistake.

Abstract

Kant reasoned that the principle of mass conservation is a
synthetic a priori judgement that we can obtain independently of experience.
So it cannot be falsified by experiments.
Kant: During all transformations of the physical reality the quantity of matter remains unaltered.
Einstein argued that mass conservation is not a necessary norm that physics has to obey but an empirical result that can be falsified a posteriori.
Einstein’s alleged falsification of mass conservation exhibits his assertion:
Atomic parts together possess a mass that is greater than the mass of the atom as wholeness. Or the parts are heavier than the whole thing.
This mass difference is the famous mass defect Δm.

According to Kant this is an error. Not an empirical principle of mass conservation is violated but the odd mass values that Einstein makes use of are faulty. The principle of mass conservation reobtains its glory! If there is no mass defect, then one cannot calculate the atomic binding energy according to EB = Δmc2

It can be showed why Mass Spectrometry fails to determine real mass values.
Unambiguous direct proof of falsity of MS-mass values:
Isomers that consist by definition of the same atoms show different mass values.

In the 19th century chemists came to the conclusion that mass values are integer numbers: 1.00 for hydrogen, 2.00 for deuterium, 4.00 for helium etc. Therefore mass is quantized. Atoms consist of hydrogen’s.