I looked more closely at the VDC data from run 1735 (R-arm). The basic spectra look all fine, but the hit efficiency in all planes seems to be very low. Only a fraction of 2-5% of triggers appear to have any hits in any of the VDC planes. This explains the very low track yield for this run.
There could be a real VDC efficiency problem (check HV, discriminator thresholds), or the trigger is malformed (triggers on non-tracks, or maybe triggers badly out of time).