Had a road trip today - new discoveries! The dynamic drive/malfunction lights are not affected at all by cycling the DSC, as suggested. They remain sporadic for in town short trips, but are absolutely absent on a sustained road trip.
Makes me visualize a marginally effective 'pump', if there is one separate from the power steering pump. Thoughts? I grant I do not know the mechanics of the DTC / DSC system, but it appears to me that hiway speeds generate sufficient fluid pressure to make the systems work, but short trips do not. The light clears consistently with only 3 or 4 miles at speed.