You have an earth leakage on your freezer greater than 30mA. Not uncommon for older class 1 appliances to fail this way.
Overloading would trip the breaker not the GFI so it's not that, unless it's a combined trip like an RCBO. In any case that would usually take some time to trip.
Be happy that you have a GFI, that saved you getting a shock from the freezer.
It may be degraded wiring if your lucky, or it may be a faulty compressor. In any case time to call the appliance repair man.