Rancho K59 Thermostat not cutting out

I have a bit of an odd situation.

I have ordered a replacement thermostat for my fridge from 2 different supplier but this issue seems the same. The stat doesn’t cut out ever and the fridge gets iced up

Fridge is a drawer fridge NCD 191L from hotpoint

Thermostat is

K59
Part Number J00155457
Ref: C00140702

Even if I put the that in a freezer (as oppposed to in my fridge) it doesn’h cut out. I cant hear it click.

The original part I replaced when I adjusted one of the screws I could make it click in and out but it seemed unreliable

Could there be a generic manufacturing fault at Rancho themselves

Literature seems to indicate you don’t adjust these yourselves

Generally with a stat I expect to find in its temperature range a case where it will click out at room temperature…

Any ideas folks….

Cheers

Gav