There's not a grocer born that doesn't overload a produce case!!!!
You can't stop them and health (temperature) inspectors know that
They stack it up for impulse buying almost 2 feet out of the air flow
then all the cold air falls on the floor and none makes it to the top shelf
My IR thermo shows 59 to 60 at times on produce
Give them a picture of max load lines and they smile at you and then
as soon as you leave they overload the case so they won't get fired
Some would rather stock a non refrig product on the top shelf so they
can continue overloading the lower shelves and dump horsepower on the
floor but it makes a good cold display for beer on sale on the floor LOL
If one fan motor has failed they all have to be replaced as they have
the same hours history on the bearings and you can't see lowered rpms
and don't allow any bent blades which do cause lower rpms = lower cfms
If you unloaded and power washed all possible air flow restriction areas
replace all fan motors, check for correct blades and
balance the blades
If the motors are replaced I increase wattage size to at least 9w if smaller
than (4 or 6watt) that, check superheat and coil temp defrost clock and
mfg settings, check the R-22 compressor for blow by caused by case
overloading for 5 years then remark case load limit lines and call it a day