This is a recurring problem that appears regularly in this newsgroup.
My 30 year old Moffat fridge acted up again. The fridge compartment
won't get cold enough and the milk curdles. The veggies yellow
faster. I don't eat the usual packaged foods so there's no problem of
any spoiling.

For years the solution was to switch off the fridge and leave both the
fridge door and the freezer compartment door open overnight to let it
defrost fully. This time it didn't work and it was very obvious that
there was still a chunk of ice behind the freezer compartment wall
that didn't quite thaw even after 24 hours (room temp 66 deg F).
This "fix" after defrosting but acting up again had been happening
more frequently and between shorter intervals of late. I didn't want
this remove the food and defrost routine again.

After 30 years service and I was willing to risk messing with it to
get a permanent fix. At worst I will buy a new fridge.

The design philosophy of any consumer product is simplicity, easy to
assemble and easy to disassemble and service. A good look at the
freezer compartment suggested that the floor panel was snucked under
the front bezel and held in flat by two plastic corner studs. I
couldn't push in or remove the 1/4 inch studs but in the process
pushed inwards the side panels. That's it. I pushed in the side
panel far enough for the floor panel to pop up over the stud (repeat
for the other side.) There were ventillation holes large enough to
slip in two fingers to pull up the bottom panel and slide it out from
under the front bezel. Another tug and the panel came off the back
end too. The back panel was held in place by four screws and it comes
off easily.

Sure enough. The bottom run of coils behind the back panel was solid
ice. This took another four hours to defrost fully. I took the
opportunity to clean up the fridge, (wet) sand off the rust at the
panel line where the ice blockage was and seal that with a smear of
white silicone. I had thought of spray painting that but decided
silicone was more effective and actually cheaper and faster drying.

After reassembly the fridge works great.