On a GE UltraFast Combo, error 18 and the Check and Clean Drain Pump Filter alert point to the drain and the pump filter. They are not lint filter warnings.
Water left behind that lengthens drying
The manufacturer documentation links the cleaning alert to drain restrictions and code 18 to the pump filter. A load that finishes very wet can make the following drying cycle take longer, but by itself it does not confirm a pump fault.
Check the correct filter
Find the pump filter section in the UltraFast Combo manual. Stop the appliance, disconnect it safely, and wait for the water to cool. Prepare for the draining step indicated before opening the cap: there may be more water inside than is visible through the door.
Remove only accessible objects and debris, check the seating, and reinstall the filter so it seals tightly. Also check the hose and how far it is inserted into the household drain according to the model diagram. The guide to drain filter cleaning explains the pre-drain step.
If the error returns with the accessible path clear, request service. Do not disassemble the internal circuit or clean the air filter as the only response to 18.
Report whether the problem appears during draining, at the end of the wash, or only as longer drying time.