frost-free freezers have ducts behind the back wall, and a fan blows cold air through these.
They are prone to blocking with ice. Once an ice block has started it get bigger and bigger.
You have to turn the machine off, take all the food out and eat it, and leave the door open for at least 24 hours or until it has stopped dripping, inside and out and including into the dish on top of the motor (you will have to pull it away from the wall to see this. clean the dish out, it may be dirty and mouldy).
If you plug it back in before all the ice has melted and dripped out, you have wasted your time.
Leaving the door partly open may cause this. It will also happen if the defrost heaters are not working. If you fully defrost it, see if it happens again, and how long it takes. If it happens quickly, the machine could be repaired, if you think the cost is worthwhile. If it takes a year or so, you might be willing to do an annual manual defrost and save your money.