I have not tried to reproduce. I am only speculating as to the issue.
I did a little reverse engineering on your channel and it looks like when you request a folder, you pass the entire path to the server: C:\...
1) that path is going over the http url length limit
2) that path has some funky characters that are not being properly url encoded
3) the path has no funky character and the url length limit isn't reached, but the python server is hitting a limitation that is less than the url length limit
I'd recommend that dellsweig send you the full path to a file that doesn't work so that you can set up the same in your environment for testing. He can do this without any roku changes. If on windows, browse to the mp3 he's trying to play or folder he's trying to open, copy the "address" and send it to you. You could use that to recreate the same thing on your PC.
This does not play:
K:\Media Files\Grateful Dead\Live Dead Shows\1972\Grateful Dead Live Amsterdam Concertgebouw 5.10.72\gd72-05-10d1t01_vbr.mp3
This plays just fine