coupling of 2 identical PMSM

Mechanically coupled two identical PMSM motors back-to-back. One operates as a motor (driving the system), and the other operates as a generator (loading the system). In theory, the electrical power drawn by the motor from the DC bus should be nearly equal to the electrical power regenerated by the generator back into the DC bus (the difference being only the system losses).

However, as the load increases, the generator’s DC bus current becomes noticeably very smaller than the motor’s DC bus current.

simulated this setup in MATLAB 2024a and attached the simulation file for reference.What could be the reason for this imbalance?