After 4 years of use without problems , I don't see you have any justification for a complaint. We also have the fridge next to the cooker ( as does almost everyone I know) never had a problem since we got the fridge 8 years ago. As said, the cooker is only on an hour or less most days. I agree with bhg , more likely to be the current very hot weather than anything to do with being next to the cooker.(we are getting very near to breaking the record for the hottest ever day in Europe!) Is there some free space behind the fridge so that the hot coils that dispel the heat from inside the fridge can get cool?
Lack of enough space to let the fridge coils cool can be a problem.