Check the proximity switches for the double arm to make sure they are triggering at the correct position. Make sure no chips are causing switch to trigger early. If this is something new that just came up, I would strongly suggest not making any parameter changes affecting the timing of the tool changer arm. Search for a mechanical cause.
Use the T/C Recovery page to manually cycle through a tool change and watch the diagnostic bits displayed to verify its position when the switches change state.
Good luck and let me know how you make out.