Alarm going off and losing sound on one side

I'm wondering if I have a dicky connection in my drivers door wiring. 

I've noticed a few times that I've lost sound from the speaker on that side.  And recently the alarm has been going off for no apparent reason, multiple times on the same day, yet nothing other days.

It went off 4 times in a row at the weekend, and when I checked inside it i noticed that the speaker wasn't working again.  I slammed the door and opened it.  Speaker now working,  alarm didn't go off again. Same thing this morning.  Alarm went off multiple times,  I slammed the door and it didn't go off again.

So my question is, is this bit of wiring between the car and door something that can be easily replaced, and is there any way (ideally without VCDS) to find out why the alarm sounded?

My assumption is that the intermittent fault on the wiring is making the alarm sensor think the door is being opened or something.

Many thanks