I just found one, service SE 28166 from Stuttgart to Bietigheim-Bissingen, and tested it. It consists of a Wittenberger cab, 4 Dostos and a 111. And I can confirm that neither the OHLE voltage meter nor the Oberstrom meter nor the traction indicator seem to work in the Wittenberger cab, when coupled with Dostos. I ran back to the loco to check if it was set to ZWS (it was), and there the OHLE voltage meter showed the correct value. Very peculiar...