Homematic Binding: "Channel not found for datapoint" errors for definitely existing channels

Sorry for this beginner question but how can I install the snapshot build of the homematic binding? I followed the instructions in the FAQs, however after restarting openHAB the old version 2.1.0 seems to be pulled in as well (it was “Uninstalled” before restarting openHAB!):

openhab> feature:list|grep -i homematic
openhab-binding-homematic                   | 2.1.0            | x        | Started     | addons-2.1.0                | Homematic Binding

openhab> bundle:list|grep -i homematic
235 | Active    |  80 | 2.2.0.201711012040     | Homematic Binding
237 | Installed |  80 | 2.1.0                  | Homematic Binding

REST shows me a 404 on my Homematic things in this situation.