Obscure Failure Reason on Zipping a Package

I found an obscure failure within Windchill PDMLink functionality to note.

System:  Windchill 10.2 M030 (CPS08)

If a failure is observed when trying to zip a Windchill package and the Windchill system's header appearance has been customized, make sure that the file "left_gradient.png" (an OOTB file) still exists, with its original file name, at its original location of <WC_HOME>\codebase\netmarkets\themes\windchill\Header.  Without this file, the package will fail to zip (check the Event Manager after the zip operation to check status) and the MethodServer log may indicate a "file not found" error on this file.

Very obscure and odd given the lack of connection between packages and header customization!