Re: mistral frost free
9/10 times ice build up in freezer blocking off air ducts to fridge.
First step is to check the freezer door seal.Does it seal against the cabinet all the way around.Look closely at the bottom corners of the seal as you close it are they pushed or folded in thus not making a proper seal.Any gaps in the seal against the cabinet will cause warm air to enter the freezer casuing ice to build up.
If its ok try and defrost it with the plug turned off and baskets out,doors left open for at least 12 hours.Ice will be behind the panels that you can’t see.
After defrost dry everything up and turn on.
This would be my first step.