It sounds like the evaporator tray is overflowing, when cold air in the fridge condenses it creates water. This water runs down the back of the fridge panel and into a gully which goes to a condensation pipe which displaces the water into a evaporation tray, where the water is heated by excess heat by the compressor which should result it in evaporating.
Pull out the appliance, and just above the black compressor should be a evaporation tray which has water in it, and above that a condensation pipe which goes through the middle of the appliance.
Check the tray is well seated and not cracked, which can be found on top of the compressor, and the pipe is correctly aligned to collect water expelled from it, and not blocked. You may find the video here useful.