Weird, just spent a good ten minutes in my server playing with the FxPlane object, I couldn't replicate your issue.. Is the FxPlane object you're creating really assigned to the variable %obj? Are you working with multiple objects in your code, because if you are make sure to check that you're setting the field isSolid to true on the right object. Could you post some code if you still can't figure out what is causing your issue?