Can you provide more details? I don't use weld beads (ever), but this quick test worked OK.
SolidWorks 2017. Simple two body part, with weld bead added down a central chamfer.
Exported the part as a parasolid, read it into Keyshot 6. Three bodies were in the scene tree.
What version of keyshot?
Try a test and import my parasolid model from above into Keyshot. Does the weld bead show up in the scene tree?
What version of solidworks?
I don't recall any changes in how weld beads were created, but I never use them. If you check the solidworks feature tree, are the weld beads solid parts or solid bodies? I'm pretty sure Keyshot will import the surfaces as well, but it might help narrow down the cause.