Accessing and releasing the electrical lock pin secured connectors, DIY repair, why unit stopped working/cooling/freezing, how to prevent future failure

Again, noisy "clonk" or "tap" relay sound replace relay asap. New relay should make a "click". I also have a 18ft-cu fridge with failed relay - it has a different model of relay
To resume: replace first start relay alone, if compressor doesn't start, replace overheat relay as well. If compressor still won't start, either compressor is worn or there is another problem (for example, failed thermostat sensor)

Two failure scenarios:
1. compressor runs for too long and overheats - normally the overheat relay will disengage and stop it.
2. compressor doesn't start - either relay failed to start it, either compressor ran for too long and the overheat relay disengaged and stopped the compressor.
In both situations, I suggest buying both relays, replace first the start relay, if compressor doesn't start, replace the overheat relay as well.

Obviously, there is also the "normal" wear of the compressor. I can tell on these recent appliances, the compressor oil is poor quality and will degrade after only 2-4 years, depending how often you open the door and put uncooled items inside. Compressor oil is simply not strong enough to take extended compressor operation. That's another reason why these fail so soon. When the oil degrades, the compressor is loosing pressure and will take longer to cool down which in turns causes the compressor to overheat even more and accelerate the wear.

Tip: while waiting for new relay, manually plug freezer in for 20 minutes every 3-4 hours or so, it should be enough to keep items if not frozen, at least cold for several days. Use a timer with alarm, so you don't forget the unit running for too long (will wear off the compressor). This will not work for fridges (won't say cool enough).

Depending on the unit, a fridge/freezer may start right away after being plugged in, or afte a 30 minutes or so delay.

The start/stop relay on small "hotel room' fridges has either 1 or 3 connectors and is usually marked as QP2-4R7 PTC 4.7 Ohm 110V (for North America). The top smaller overload/overheat relay depends on the size of the compressor HP - my compressor has 1/2HP with part code 6750C-0005P. It is important to have the right overload relay, to prevent the compressor from overheating/damage in case the start/stop relay fails while the compressor is running. The overheat realy is basically a temperature fuse: if the compressor overheats, this relay burns the fuse and stops the compressor - this overheat relay then needs replaced with new one in order to restart the compressor.

When you start a fridge/freezer that is no longer cold, it may run for fairly long time. I suggest making sure the compressor doesn't overheat during this time. May want to place a room fan right in front of the compressor. Alternately, may want to stop the unit manually (unplug), and restart it until it reaches cold temperature without overheating the compressor. If the compressor feels hot after running from cold for only 25 minutes, it means the oil is degraded and the compressor is now quite worn.