Quick take
Check the drain path, filter, setpoint and ambient temperature before assuming the compressor has failed. In a wet crawlspace, air sealing and moisture-source control matter as much as dehumidifier capacity.
Not reaching target humidity
An undersized unit, open vents, groundwater or major air leakage can overwhelm the dehumidifier.
Drainage problems
A gravity drain needs continuous downward slope. Pump-assisted setups introduce a separate pump and tubing failure point.
Icing and low temperature
Cold crawlspaces can push the unit into defrost behavior and reduce moisture-removal capacity.
Airflow and filter
A dirty filter or blocked inlet/outlet reduces performance and can make a correctly sized unit look weak.