Removing a switch (optima XM)?

The situation I have is that zone 3 was activating at random and I had to loop It out so that I didn’t have to omit it every time I set the alarm. A few months on now and I want to look at sorting this problem out.

What happens is I have a window and door catch connected to Zone 3. The wire come from the box upstairs and under the floorboards it then splits and goes in two directions and one down to the window and one down to the door. It appears that the cable was cut and connected together and then taped back up. This is where the original problem will have been as the connection was cutting and causing the alarm to activate. The problem I now have is that this “join” is under some laminate that I cannot get to without ripping the floors up, taking skirting up and ruining the new wall paper I did the other month. After a lot of messing about I am now left with 1 cable coming from the control box to nothing the broken end is on the floor. I window switch with the cable running inside the wall and ending somewhere under the floor where I can not get to. Finally I have a door switch (same as the window switch) running form the door inside the wall and then inside trunking ending near the cable form the control box. All these cable are 4 core (red, yellow, black and blue)

My thinking was that I could I simply join the cable from the control box to the cable to the door together matching the colours and insulating each one from each other and the control box would see this as 1 switch. I could then at a later date either rip the floor s up and rescue the window cable or re connect form the back door switch as and when I decorate the room, hiding cables accordingly.

The alarm contractor came round tonight and looked at the situation and when I explained it he said that should work, he then didn’t charge me as he said it was an easy job for me to do and left, after checking that the switches were wire correctly at the door and window. Great I thought.

I have just done what I said above and am still getting zone 3 coming up as tamper / alarm when I set the alarm.

If you are still following this and can offer any thoughts or help I would be most grateful and will try in some way to make it up to you.

Cheers in advance