I will answer this from a SS POV.
Failing to supervise a young child, is neglect.
This can mean then being closed in a room and not ensuring their safety by leaving dangerous objects around.
One incident wouldn't "flag up", unless an injury occurred.
The question is whether you look after your children depending on whether SS would intervene, or you want to care for them in a way that means they won't come to harm.
A & E are filled with toddlers with injuries failing on objects, these get questioned.
Yes accidents happen, but why you wouldn't want to prevent these accidents, wherever possible, I don't really understand.
First time parents make mistakes, by your third, you know what they capable if/what can happen.
It isn't your DH that will have to live with a serious eye injury, or brain injury, after over heating and fitting.
These happen every day, they just aren't reported in the press.
Accidents to young children should happen because the Carer is to lazy or CBA to look after the child.
Laziness and not caring enough to prevent an accident is neglect.