Oh gosh. The reason I haven't answered this message is because I know little to nothing about using the commandline. Well I mean, I guess that little bit of code you showed is the commands for the commandline?
Do I understand correctly that it seems to work only when you view it with Firefox? That would give me the impression that it's working, that Inkscape is applying the pattern correctly, but that the problem is happening with whatever you're using the view the file.
Hmmm yes, the message you referenced seems to indicate the problem is related to the viewer as well.
As to why it works when a rectangle is used but not with a path, I don't know.
Or is this a problem with using the commandline? If you do this with the gui, do you have the same problem?
Unfortunately, I can't seem to keep my eyes propped open tonight. But I'll be back tomorrow, and be ready to try testing using the gui. Or otherwise at least I'll be able to think a bit more clearly.