Costa Coffee review: Baby changing door lock

I was in the baby changing toilet with my little girl, after sorting her I used the toilet that was available.
I had a problem locking the door, it was a big heavy sliding door and a lift handle up to lock. However it never caught on to actually lock the door.
When using the toilet another customer managed to slide the door open when it was supposed to be in the lock position. I was left feeling embarrassed and had to actually remove myself from the loo to close the door over.
I complained to an employee which his reply was that they had previous complaints about it. Obviously nothing has been done since those complaints.