  We study theoretically the two-center interferences occurring in high
harmonic generation from diatomic molecules. By solving the time-dependent
Schroedinger equation, either numerically or with the molecular strong-field
approximation, we show that the electron dynamics results in a strong spectral
smoothing of the interference, depending on the value and sign of the driving
laser field at recombination. Strikingly, the associated phase-jumps are in
opposite directions for the short and long trajectories. In these conditions,
the harmonic emission is not simply proportional to the recombination dipole
any more. This has important consequences in high harmonic spectroscopy, e.g.,
for accessing the molecular-frame recombination dipole in amplitude and phase.
