I have a MMU and the Original Enclosure, but I don't use any special Filament Buffer. I have enough space, so that the filament can relax freely outside of the enclosure.
With this mod of the original transport handle, you easily guide the filament into the enclosure.
You need 5x PC4-M10 connectors, that let the PTFE through the PC4. Just push the ptfe tube just down to the very end.
The author remixed this model.
Use the original handle to guide 5 different filaments into the box.