If neither of these are the case, the unit may have a refrigerant leak that needs attention however, this is usually very rare unless some sort of damage has been done to the unit.

Whirlpool does have a service manual for their 'under-counter' icemakers. You can find it at the site linked below.

I have never worked on any of the Whirlpool ice machines but I do believe your problem may be linked to a cooling system problem.

If this unit uses a forced air condenser, the condenser could be plugged with dust or pet hair or the fan motor may be slowing do to defect. Either of these conditions will hamper the ability of the appliance to remove heat and may cause the symptoms you described.