X crash with 1 finger subscriptions

To reproduce use the Geis v2 advanced interface and subscribe to 1 finger gestures (touch and flick tested).
When touching the window with 3 or more fingers simultaneously I get the following crash (including some leading logs from geis):

    GEIS(debug)-geis_backend_multiplexor_pump:411 activity 0x1 on fd 17 callback_info=0x166fb10
    GEIS(debug)-geis_backend_multiplexor_pump:411 activity 0x1 on fd 18 callback_info=0x1670170
    GEIS(debug)-geis_backend_multiplexor_pump:411 activity 0x1 on fd 17 callback_info=0x166fb10
    GEIS(debug)-geis_backend_multiplexor_pump:411 activity 0x1 on fd 18 callback_info=0x1670170
    GEIS(debug)-geis_backend_multiplexor_pump:411 activity 0x1 on fd 17 callback_info=0x166fb10
    X Error of failed request: BadAccess (attempt to access private resource denied)
      Major opcode of failed request: 131 (XInputExtension)
      Minor opcode of failed request: 53 ()
      Serial number of failed request: 41
      Current serial number in output stream: 43
    GEIS(debug)-_subscription_destroy:425 destroying subscription "1fingerGestures" id 0
    GEIS(debug)-geis_backend_token_deactivate:75 called
    X Error of failed request: BadAccess (attempt to access private resource denied)
      Major opcode of failed request: 131 (XInputExtension)
      Minor opcode of failed request: 53 ()
      Serial number of failed request: 42
      Current serial number in output stream: 44

Which kills the window.

The crash doesn't happen when fingers are added to the window one at time; the application can handle > 10 simultaneous touches, just not when the are added at the same time.
It doesn't appear to happen when only subscribing to 2 or more finger gestures.

More info in this question: https://answers.launchpad.net/geis/+question/270060