"Brian Gaff" wrote in message
...
Older freezers were not as well insulated and insulation can go leaky over
time due to ingress of damp or any kind of seal issue. I'd have thought
that -12 if confirmed is probably just the self defrosting. Mine does this
and nothing has poisoned me as yet.

I too work on the basis of "I've not been poisoned yet so it must be OK".
The fact that the temperature returns to -18 after a hour or so and that it
isn't worse when the kitchen ambient temperature is warmer, suggests that
it's not leaky seals. Ice cream shows no sign of large ice crystals that
you get if it's partly thawed.

Odd that we've only started noticing it recently, when I presume its been
doing its self-defrosting cycles for the past 2 months since we've lived
here. Perhaps we're just not very observant...