I remember having some issues, but not specifically this one, when we started working on our drawing automation. We pull all of our drawings from PDMLink, so we don't have this issue. Have you tried using quotation marks when you call the path?
Design well!
We pull template parts, assemblies, skeleton parts, and drawings (not formats) directly from PDMLink. They do not have to be in the workspace and you do not have to provide a path, just the number and extension using the RETREIVE_MDL command.
Design well!