Automation control point problem in A3

I have a problem with A3's control point creation, eg. when editing gain
envelopes. Clicking to create a new control point adds two points instead
of the expected single point. Manually deleting the second point every time
is too much of a slowdown in work flow.

If someone could give me a pointer to which file(s) in the 3.0 code determine
this behaviour I'd appreciate it.

John