Samsung srs535 leaking defrost water

I have a Samsung SRS535 SIDE BY SIDE FRIDGE/FREEZER approx 4 years old and started leaking defrost water from the floor of the freezer several weeks ago for the first time.
I removed the lining from inside the freezer and thawed the ice from the drip tray (see enclosed picture), with a hair dryer however the thawed water did not flow through to the flexible hose to the evaporation tray located under the heat exchanger coils in the freezer base. I removed the flexible hose and it was not blocked. I then poked a wooden skewer up the flange that the flexible pipe goes onto only to feel something spongy. but could not remove it. The three holes in the drip tray do not line up to any direct path to the flexible hose
It appears to me the freezer is working correctly, defrosting as it should, but the defrsted water is not getting away to the evaporation tray. There appears to be no blockage in the path of the defrost water.

Hoping you can assist

Barrieb, When the tray is free of ice, there will still ice in the drain line insulated section before it exits out the back. Use hot water then a cabletie or an item semi rigid to move the hot water in the drain from the freezer side. This could take some time as there is ice + frozen obstruction to move. It will eventually clear then run near boiling water through it. DON'T cut yourself on the aluminium fins of evaporator.. mike.

Mikeref, I defrosted the freezer side again today - mopped up the defrost water with a towel to reveal the three small drain holes in the drip tray below the defrost heater and poured boiling water in there 4 times over a period of three hours. I had to mop the water up each time as it did not flow away.
In looking through the holes in the drip metal tray there is a 1" round hole in the plastic freezer lining base so inserted a cabletie in there but it would only go about 1.5" and then struck something solid. it does not seem to be a direct flow path to the flexy hose.
There was no evidence of any moisture in the plastic flange at the back of the freezer.
There must have also been a mal function within the last couple of weeks in the heater? or some other defrost controller for this to start happening?

Barrieb, three hours is a long time defrosting, takes max 20mins on this configuration with hot water. Many cases of peas or carrot pieces ending up caught in drain, then freeze with ice backing up and overflowing. Deice again and this time remove flex outlet and with small air compressor at no more than 30 psi/ 240kpa,(hope you can get your hands on one), backflush drainline. I wouldn't be suprised if this brand snaked the drain before exit. Drain blockage can be frustrating...mike.