Electrolux ER2656B noise

First my cooker now the fridge freezer has joined the list of failing appliances.

Model is Electrolux ER2656B the gas is R134A (75g)

The fridge freezer is a frost free model, and about 6 or 7 months ago it started to make a loud noise, it is difficult to describe. It is like there is a low kind of rumble (almost inaudible) when the motor kicks in followed by a loud dry squeal (kind of like the sound of air coming out of a balloon or a table being dragged across a hard floor) the noise is not perminant and will come and go. It goes away for months then it will come back for a few days.

Whilst making the noise I can tip the fridge freezer and it would appear to somtimes stop the noise for a while. I have been told it may be the gas but there should be hot spots in the freezer, which I have not noticed.

Any Ideas?? The last engineer I spoke to said they needed to hear the sound.

Cheers Dan.