I think the problem remains open because when a supercrrent slowly decays, the resistivity can remain negligible and diamagnetic signal is strong. Thus, the decay looks like a usual SC state.
We may also modify the experiment. We can create a small non-SC area directly on the ring surface, a point with magnetic field killing the pairs only in this small area. Then we should see the same effect - pair creation/annihilation and pair exchange between the small non-SC area and large SC...
I believe the supercurrent will decay in the experiment. Because the new pairs (created in the wire and diffused toward the ring) never experienced EMF. Only the experiment can show the real behaviour of the system.
All basics are derived by the assumption that SC pairs can be created/annihilated below Tc, so all conventional arguments follow from the conventional paradigm. Whereas the constant pair density follows directly from conservation law and thermodinamics. And from the reasonable idea that...
Moreover, assuming that pairs absorb any thermal energy we must accept that the pairs also emit any thermal energy. That is exactly named - momentum dissipation. The pair absorbing/emitting is no longer in its ground state and, thus, can dissipate energy and momentum
Closely to Tc the pair density tends to zero, so the velocity of remaining pairs should strongly increase (in order to keep the current stable). Thermal energy kT is quanized and cannot strongly accelerate each remaining pair. Or we must do a new assumption that each remaining pair can absorb a...
To solve the problem, I proposed a simple experiment about pair permanency, see
https://www.researchgate.net/publication/373756657_Tuning_of_Lifetime_of_Cooper_pairs_in_a_Massive_Aluminum_Ring?channel=doi&linkId=64fad8fb05a98c1b63fca0db&showFulltext=true
Maybe we will see one day the result.
When we guess that the pair density changes abruptly at Tc, then all contradictions vanish. Moreover, observations on metals say - the transition at Tc is rather abrupt than smooth. So I'm sure the pair density cannot smoothly decrease below Tc.
The momentum taken by lattice is partially converted into heat, because the lattice is much heavier than electrons.
If mv=MV and m<<V, then mv^2 >> MV^2.
The heat cannot be spontaneously converted into an ordered momentum again. Thus, the part of the supercurrent momentum is lost for ever.
The contradiction is that the newly generated normal electrons slow down due to collisions with the lattice and, thus, transfer their angular momentum to the lattice, whereas the supercurrent momentum remains constant. A clear violation of the conservation law for angular momentum.
You wrote - "the newly generated normal conducting electrons need time to loose their current in collisions with the lattice"
A contradiction again : the magnetic field changes and generates an electric field because the current is actually decreasing, that is newly generated normal conducting...
Exactly. The angular momentum conservation works in superconductors at warming. Annihilated pairs give their momentum to lattice, and then the supercurrent momentum must decrease. However, the supercurrent remains constant. Conclusion: the pairs don't annihilate at warming.