Help preventing fridge ice

UPDATE - I think I fixed it: comment link

Hi

After a thermostat / potentiometer replacement, my fridge produces ice / snow at the back even on the minimum ("min" setting, the one next to OFF).

The thermostat was replaced because the fridge just never turned on anymore.

The cooling plate is INSIDE the fridge because the one in the back wall of the fridge no longer worked. The same person did this too and worked for years with no ice, and we were really happy with it.

I thought this was caused by a clogged drain pipe so I found it, chopped it off completely because it was a botch job (or seemed like it) and replaced it with a catcher so the water still falls in the evaporator tray

Before:

Cleaned it with a long cable and by pouring water with dish detergent down the hole...

After:

But the ice formed back to the same amount within 1-2 weeks :-/

I took apart the old thermostat and found that it has these 2 screws in it.

I destroyed the whole thing to take out the screws completely from inside it, but I could turn them from outside too. What is the use of these? Can I adjust the cooling by turning them somehow?

I suspect that the fridge is now cooling more, therefore is creating more ice. What else could be the issue?

This ice did not use to form before the thermostat replacement.

The fridge / freezer is about 20 years old I think. It's labeled Arctic but according to the guy that fixed it for us, it's actually a rebadge, but I don't remember exactly what brand he said it was. May have been Gorenje or Beko. It has 2 compressors for the fridge and freezer and they're completely separate from each other.

Ideas?