Let me make sure I understand the problem.
Matt, you have a Rhino5 file with named objects, you write it as STEP, read it into Solidworks, and the objects are not named correctly. However, if you read that STEP file into Rhino4, the names are OK there. Are they OK if you read it into Rhino5?
Dan, you are saying that if you write a STEP file from Solidworks, the names do not show up correctly when you read it into Rhino5 but it was OK in Rhino4.
There are several places that an object’s name can be stored in a STEP file. It seems Rhino and Solidworks use different places. I’ll just have to figure out which one Solidworks uses.
Matt, can you send me (firstname.lastname@example.org) a simple 3dm file that has the problem?