Central locking keeps locking itself

[Spoonaltap]

My pug has developed an annoying fault, the car just keeps locking itself. Sometimes it does it as soon as you unlock it sometimes it's a few minutes. Seems to be getting more often, it developed this fault a few months ago but sorted itself but now it's back. Started doing it after I loaded some rims into my boot, lowered back seats and I think it started doing it last time after having stuff in the back as well. Checked and my locking unit isn't under the seat I don't think so maybe just a coincidence.

My keyfob doesn't working, well it does but drains batteries in a day so I unlock it with the key.

Any help would be good as it's super annoying.