20 year old Amana upright water drain problem?

Does anyone know how to remove the shelf that separates the freezer compartment from the refrigerator area to be able to access the drain hole the water is supposed to drain into?

This is a standard 20 cubic foot upright top freezer and I have tried everything to clear the drain line. The water eventually comes out in the refrigerator through the slots in the refrigerator ceiling, which is actually the freezer floor, and I have to have a little bucket hanging in the refrigerator to catch the water or it would wet the food. It will not come out where it should in the removable water drain pan at the very bottom left of the refrigerator.

I took a small tire inflating compressor and blew as much air as I could up the drain line. Every time I do this, this causes the water to slowly start dripping every time and eventually it all comes out as it should. I do this when I know the refrigerator has not been running for awhile and most likely melting the water off the plates in defrost mode.

Even though this temporarily seems to fix it every time, in a week or two it plugs right back up again and I have to do the same thing again.

I can't figure out how to get the freezer floor out so I can clean whatever the blockage or gunk is that keeps blocking the hole. I can move it back and forth slightly but something is preventing it from coming out.

If I could get that out, I could see what is in that space between the freezer floor and the refrigerator ceiling where the water eventually accumulates and I'm sure I could fix it. Instead of the water going into the drain hole and coming out at the bottom of the refrigerator, it comes out wherever it can get out.

I can't see any way to access anything from the back. And even when I take the cover off inside the freezer on the back wall of the freezer which gives me access to the defrost motor and the fin plates, I still can't see the drain hole. Nor will that corrugated plastic floor liner come out.

Any refrigerator water drain experts advice on how to remove that freezer floor panel would be greatly appreciated.

The model is TQ20 NBL.