When creating a DPX sequence from an Avid MIxdown the DPX frame naming is being truncated (clipping off the the tail of the naming). source name = SHO_18022_VAM_522337.MXF the resulting DPX name = SHO_18022_VAM_084240.DPX. This problem was reported in version 3.1.3-b11597
Sorry, the fix didn't make it into the initial 4.0.1 release. It will be in the next one, which likely be in a few days.