HRESULT: 0x80210006
is WIA_ERROR_BUSY
.
From the WIA API Error Codes page:
WIA_ERROR_BUSY The WIA device is busy.
According to Communicating with a WIA Device in Multiple Threads or Applications, it looks like something else may be accessing the device:
If a thread currently has a device locked (it is actively communicating with that device) and another thread attempts to call a method that actively communicates with the device, the method returns a
WIA_ERROR_BUSY
error.