Probable Cause:
Unbalanced system, load in excess of design conditions.
Compressor discharge valve leaking.
Leaking hot gas defrost solenoid/hot gas bypass valve.
Hot gas bypass regulator piped direct to suction, without a liquid injection TEV.
Remedy:
Balance system components for the necessary load requirements.
Repair or replace valve.
Check and replace hot gas bypass valves if required.
Install properly sized ALCO LCL liquid injection thermo valve.