python 333 and dei 530t

I've just finished installing a Python 333 alarm and DEI 530T window module into an Australian Holden Commodore. It's all working sweet except when the windows are fully down and you arm the alarm the doors will lock but then unlock again. The windows close fine and you can lock the doors by pressing the arm button on the remote again. The windows are set up as a + trigger and the 530T is triggered by the orange -500ma wire from the alarm. I've also got the orange wire triggering a relay which I'm using as a 2nd immobiliser and there is a 1amp diode installed inline to the window module. The door locks are also + trigger and are controlled by the inbuilt relays in the alarm.

Is there any reason for the doors to lock and unlock or is there a fault somewhere?

So it only does the lock /unlock when the windows are down? How many pulses is the Python set to for the lock. Also you should use a diode for each item connected to the -500ma wire. Also verify that the windows are not back feeding the Acc. circuit and triggering the unlock that way.

First diagnostic, remove the 530t fuse with the windows down and then see what happens.
Was the Commodore the same as the Vauxhall/Opel version?
If so the locks were NEG (-) BROWN / red lock, BROWN / white unlock BROWN / black TOTAL CLOSE - thus no need for window closers.
The symptom sounds more like a faulty microswitch in one of the front motors to me.

Two common faults on that car.
1)Anti trap on the windows kept failing.
2)Problems as above with the lock actuators.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.