water accumulation

I've had this fridge for a couple of years and I'm assuming some portion of the drain system from the freezer to the refrigerator is either frozen or broken but I don't know where those components are. Can anyone give me some ideas? We're finding a puddle big enough to saturate multiple bath...

Water drips from the panel (inside refrigerator section) underneath the freezer compartment. There is a drain line that exits refrigerator section through back panel. I understand it winds down to bottom of refrigerator where there is a drip pan (drain pan) non-removable. The image is taken...