Issues with a fridge and a chest freezer,

dekaspace1

The fridge used to be very good at cooling stuff and I had to put it max 4 any higher and stuff would freeze, noticed now even when at 6 (7 is max I think) things are cool but things like bottles of soft drink are room temperature within 30 minutes rather than 2 or 3 hours, I noticed one time that the top lifts off a little in one corner so I think its come unclipped (looks like it just locks in place but can't work out how) maybe this means its not sealed right?

Or could it be the pump? The issues started a few months ago when I had my gas safety check and I moved fridge (as its in front of boiler cupboard, only place I have room for it) then moved it back, I don't hear the "hum" very much anymore.

Chest freezer issues is me being stupid, I got a new one so gave old one to friend, it took 2 days to barely defrost so I put a electric heater next to it and put it too close so within about 3 minutes I heard a "pop" sound and noticed the inside of the lid (not the seal) was a bubble.

The freezer inside was still frozen solid so seemed to be keeping things cool.

Gave it to friend and noticed I left this "piug" that goes internally on the base, friend said the freezer now only freezers like a foot from the base and no higher and he tested it by putting the clip on baskets in and anything in there defrosts.

Apart from that big bubble on the inside lid everything looked fine, the seal was intact and door closed fine.

Any ideas?