Sounds as though the immoby is cutting in, I would if your competent/confident see the ignition live refference for position 2 is being received by the alarm.
If not confident I would leave alone and seek a clifford dealer, these can be reliable alarms, most probs are due to bad fitting, but the opportunity is there for problems simply as there is more to go wrong than say a simpler affair such as a toad.
tabetha