It is agreed that children unknowingly would enter the garage that has the faulty garage doors. Though you have not done any improper fix to these doors, it is possible that heavy usage of the garage doors would have worn out the cables that are part of the door design that is intended to operate by rolling up and down with the help of these cables. You never know about the root cause for the garage door to slide down the cable path as soon as you release the lock. It is only when you hire the experts working on the garage door repair you would be able to understand where the fault exists.
Of course, the cables may be worn out or else got damaged by the rats or other creatures that move around in the garage in your absence if at all you are living in the outskirts of the city. Not just in the outskirts, today you could see the rats even in the cities. So, irrespective of your location, if you suspect that the garage door cables looks abnormal in its dimensions then you should immediately call the experts to replace the cable as the garage door might anytime bang the floor when the cables miss to control the force that is applied on the garage door for it to stay open.
If you have children at home who could play around in the garage without knowing the possible risk for their life, it is advisable that you hire the experts and warn them that the situation is quite urgent and hence would need immediate service. Your request would be accepted and would be provided with best service. Once you are confirmed about the arrival of the expert, you could delegate the task of looking after children to your family members and could continue with your day plan.