OpenHAB simple Z-Wave dimmer set-up - sitemap buttons not working

I have a very basic install of OpenHAB for evaluation on a RasPi2 with openjdk-8-jre-headless, using the openhab-runtime package from the Raspbian Jessie repo (1.7.1) with openhab-addon-binding-zwave (also 1.7.1). I only have two devices in my network; an Aeon Labs Z-Stick v2 and an Aeon Labs Micro Smart Dimmer, which is connected to a simple desk lamp. Apart from some file permission issues (I had to manually chown /usr/share/webapps/static to openhab:openhab, or I would get a permission error on /usr/share/webapps/static/version on startup) it seems to work quite well, and system load isn’t too bad, idling at ~0.40.

I’ve set up two objects for the dimmer; a dimmer (“Test”), and a switch (“Test2”), and both have been bound to controls on my sitemap (a slider and a switch). When I use the switch, the light can be turned on and off, but the slider buttons don’t work properly: the decrease button doesn’t seem to do anything, and the increase button actually decreases the light (or turns it off, I can’t tell which - it goes dark anyway). When I look at the commands being sent they look like this:

http://10.0.0.120:8080/CMD?Test2=TOGGLE&__async=true&__source=waHome

Which toggles the light on and off successfully, and:

http://10.0.0.120:8080/CMD?Test=INCREASE&__async=true&__source=waHome

Which appears to turn the light off, or dims it to 0%.

However, if I send a numerical value to “Test”, it works perfectly, e.g.:

http://10.0.0.120:8080/CMD?Test=20&__async=true&__source=waHome
http://10.0.0.120:8080/CMD?Test=50&__async=true&__source=waHome
http://10.0.0.120:8080/CMD?Test=100&__async=true&__source=waHome

The light immediately responds and goes to the correct percentage. It appears that somehow the “INCREASE” command is being misinterpreted? My item configurations look like this:

Dimmer Test "Light" <slider> { zwave="2:command=SWITCH_MULTILEVEL" }

and

Switch Test2 "Light" <light> { zwave="2:command=BASIC" }