Instance detection misbehaves with some Epiphany web applications launchers desktop files

Plank 0.7.1 on GNOME Shell on Fedora 21.
The GNOME Web (Epiphany) browser allows saving a web page as an "application", which creates a .desktop file for it in ~/.local/share/applications.

The problem is that Plank, unlike gnome-shell's dash/dock, sometimes has trouble distinguishing between those custom "web app" launchers and Epiphany itself... In one case it has no problem making the difference between my "google calendar" epiphany app and epiphany, but on the other hand it is incapable of making the difference between my kanboard web app and Epiphany, grouping it under Epiphany's icon and allowing to launch unlimited instances of the app. It also means that it is impossible to launch the Epiphany browser using Plank if you started my "kanboard" epiphany web app first.

I'm guessing maybe Plank chokes on launchers with accents in their name, because the kanboard one has an "é" in the name (something like ~/.config/plank/dock1/launchers/epiphany-kanboard-foo%C3%A9bar-d8ff67ba096eef2b193493a44e6263edd64714ec.dockitem pointing to Launcher=file:///home/jeff/.local/share/applications/epiphany-kanboard-foo%C3%A9bar-d8ff67ba096eef2b193493a44e6263edd64714ec.desktop )

And indeed, in the debug output, I see this suspicious part:

[DEBUG 20:41:47.086942] [Preferences:328] Loading preferences from file '/home/jeff/.config/plank/dock1/launchers/epiphany-kanboard-fooébar-d8ff67ba096eef2b193493a44e6263edd64714ec.dockitem'

[WARN 20:41:47.087213] [ItemFactory:171] The launcher 'file:///home/jeff/.local/share/applications/epiphany-kanboard-foo%C3%A9bar-d8ff67ba096eef2b193493a44e6263edd64714ec.desktop' in dock item '/home/jeff/.config/plank/dock1/launchers/epiphany-kanboard-fooébar-d8ff67ba096eef2b193493a44e6263edd64714ec.dockitem' does not exist

Attaching a screencast.