Procedure libraries on PROPATH are searched for as directory entries
When the PROPATH includes a Procedure Library the client AVM treats the library as a directory name while searching.
The client process should not search the propath by constructing search paths from procedure libraries.
The problem can be seen with Microsoft Process Monitor (
https://docs.microsoft.com/en-us/sysinternals/downloads/procmon) that libraries such as 'OpenEdge.Core.pl' are used as directories when searching for r-code to run.
For example in the following image the OpenEdge.Core.pl library is being searched as if it's a directory while searching for ClientBuilder.r:

When ClientBuilder.r was not found in OpenEdge.Core.pl, the AVM treats
C:\Progress\117\OpenEdge.Core.pl as a directory and looks for
C:\Progress\117\OpenEdge.Core.pl\OpenEdge\Net\HTTP\ClientBuilder.r.
The r-code file is not found because the directory obviously does not exist.
This kind of search can impact performance, particularly if it is being performed on a remote drive: