Boot unlocks itself!!!

I don't know if I'm just being paranoid but was out shopping the other day and when me and the mrs got back to the car it wouldn't start because the boot was open even though we hadn't touched it... A few days later I was in the car at home taking the dash apart when all of a sudden the boot unlocks!!! When I say unlocks I mean it popped up but not open all the way if you know what I mean. Both times I had the keycard in my pocket but the boot lock button should not affect this as I have tried to see if that was the problem :/ it hasn't done it since but I don't want to run the risk of it getting worse.
 
I don't know if I'm just being paranoid but was out shopping the other day and when me and the mrs got back to the car it wouldn't start because the boot was open even though we hadn't touched it... A few days later I was in the car at home taking the dash apart when all of a sudden the boot unlocks!!! When I say unlocks I mean it popped up but not open all the way if you know what I mean. Both times I had the keycard in my pocket but the boot lock button should not affect this as I have tried to see if that was the problem :/ it hasn't done it since but I don't want to run the risk of it getting worse.
I would make sure there is no water ingress into the multiplug mate on the rear lock acuator.
 
As Chris said.

Open up the boot. Get the plastic plug/clip out at the top. Give it a good clean up and check for water in the ingress. WD-40 it up after and this should disperse any future water that gets caught around it.