there was a lot of frost buildup in the freezer probably because the flapper on the ice dispenser doesn't completely close (which may be a separate issue??) and we defrosted it a couple of days ago and it started leaking shortly after that.
OK. the back panel inside the freezer, correct? I replaced the defrost heater about 6 months ago and the coils were totally caked in ice. there's no ice buildup on the panel so the defrost heater should be working ok. So I guess we need to unload the freezer, shut down the refigerator, remove the panel, and go to work.
as for the flapper, I bought a new one from a local appliance parts store a couple of weeks ago. just the black round part for about $6 or $7. hope this is all that's needed for that.
below is a photo of the coils I took a few minutes ago. I assume the defrost drain is the copper tube at the bottom, directly below the defrost heater, even though is doesn't look like the image you sent. as you can see, the coils have a layer of frost on them but i'm told this is normal, correct?