Hi. I have a 5 yr old Kenmore 79571603012 which was apparently made by LG and the bottom freezer is too warm about 20F. The refrigerator can maintain 38F pretty well. Icemaker won't make ice and ice cream is soft. So far I have checked the following things.
Condenser fan is running and I blew out the condenser coil with compressed air
Evaporator fan is blowing in freezer and in refrigerator.
I pulled the back panel in freezer to check evap coils. There was no frost whatsoever on any of the coils. I have read that if there is no frost that it is time to shop for a new fridge. Is there any scenario where no frost can be attributed to something else beside the sealed system ? Thanks for any help.

Update: after 24 more hours freezer temp got down to 14F.
Pulled evap cover again found a thin layer of light frost on the bottom 2 or 3 coils.

Still wondering if this points to a sealed system failure only.