USB Focus dispatch error - by: Adam

Hi,
I am trying to set up a USB Focus v3 kit on a Raspberry Pi 2. Latest INDI with usbfocus 0.7 driver on the Pi and latest KStars from the PPA.
When I connect to it from Ekos, all values are reported properly, e.g. the absolute steps are shown and updated when moving the focuser with the handbox. It does however not react to any commands from Ekos and the driver output gives dispatch error messages when trying to move it through Ekos or the INDI control panel. Here is an excerpt:

2016-10-13T15:25:01: Client 0: read <newNumberVector device='USB-Focus' name='ABS_FOCUS_POSITION'>
2016-10-13T15:25:01: Driver indi_usbfocus_focuser: queuing responsible for <newNumberVector device='USB-Focus' name='ABS_FOCUS_POSITION'>
2016-10-13T15:25:01: Driver indi_usbfocus_focuser: sending <newNumberVector device="USB-Focus" name="ABS_FOCU
2016-10-13T15:25:01: Driver indi_usbfocus_focuser: indi_usbfocus_focuser dispatch error:
2016-10-13T15:25:06: Client 0: read <newNumberVector device='USB-Focus' name='ABS_FOCUS_POSITION'>
2016-10-13T15:25:06: Driver indi_usbfocus_focuser: queuing responsible for <newNumberVector device='USB-Focus' name='ABS_FOCUS_POSITION'>
2016-10-13T15:25:06: Driver indi_usbfocus_focuser: sending <newNumberVector device="USB-Focus" name="ABS_FOCU
2016-10-13T15:25:06: Driver indi_usbfocus_focuser: indi_usbfocus_focuser dispatch error: