Comelit audio intercom handset unlock button not working

[US1549]

I have just removed the keypad module (art.3188) on a comelit vandalcom audio intercom and blanked it off. I installed a siemens K42 keypad lower down on the post (as customer unwilling to pay for a replacement comelit module in excess of £400.) I stupidly forgot to take a picture of the wiring config before removing the broken comelit keypad as i assumed it was just 12vac on 2 terminals and the NO terminals for opening/closing the gate. (like every other videx setup i've worked on) The audio intercom module (art.1602) still remains in the top slot. The open/close contacts from the gate controller don't seem to run directly to the intercom as the pair that triggers opening will not work on its own - it requires 12vac on it before it will work. - I have some photos of terminals on the keypad before it was removed but i don't know how useful these will be as you can't see where things run to.

I have the system in a state where the siemens keypad is working and the call button works on the comelit intercom. However, the unlock button on the indoor handset no longer works which is the major issue.

I'm having difficulty understanding how this system works as I have never come across anything like it. One cat5 seems to run to what i think is a simplecom module. Does anyone have any knowledge of this type of comelit system? I'm struggling to find any manuals or wiring diagrams for the equipment.

Gate controller - Came Zl19N