Please, look at Feynman diagram of neutron b-decay involving heavy W- boson. One of the d-quark turns into the u-quark, emitting an electron and an antineutrino. The mechanism of this transformation is not considered. This is a weak interaction. But in truth, we cannot say what is interacting with anything here.
The Standard Model claims that the carriers of weak interaction are the vector bosons W +, W−, and Z0. The interaction of charged currents (with the participation of charged bosons W ±) leads to a change in the charges of particles and the transformation of some leptons and quarks into other leptons and quarks. The interaction of neutral currents (with the participation of the neutral boson Z0) does not change the charges of the particles and translates leptons and quarks into the same particles.
But our experience tells us that we can only transform composite things. First you need to disassemble the old particle into parts. Then reassemble it in a new way. Fundamental quarks are assumed to be structureless (we cannot break them into pieces).
Is there a contradiction here?