Wine cabinets attract service calls that end with nothing being replaced, because the machine is doing several things that would be symptoms on a different appliance. It is worth going through them, because the same observations, in slightly different form, genuinely are faults.
Condensation on the Glass
A glass door separates cool humid air from warm humid room air, and when the room dew point rises above the glass temperature, water forms. In a humid kitchen in August this is unavoidable physics, not a seal failure. It appears on the outside of the glass, it comes and goes with the weather and with how often the door has been opened, and it clears when conditions change.
The version that is not fine looks different: persistent water or frost on the inside, water pooling in the base of the cabinet, or condensation that is localised to one corner of the door and stays there. Localised means the seal is lifting at that point, usually because the hinge has settled under the weight of the glass. Water in the base usually means a blocked drain channel.
The Compressor Running for Long Stretches
A wine cabinet holds a narrow band with a lot of thermal mass behind the door. It runs long and gentle rather than short and hard, because rapid cycling is exactly what it is designed to avoid. Long run times after the cabinet has been loaded with room-temperature bottles, or on a hot day, or after the door has been open while you rearranged shelves, are expected. Give it a full day before judging.
Not fine: running constantly and never reaching setting, running constantly with the cabinet noticeably warm inside, or short-cycling every few minutes. Also not fine, and often missed, is a cabinet that runs normally because it is standing somewhere outside its rated ambient range, such as an unheated garage in winter. A cabinet that cannot cool is obvious; one that cannot keep itself warm enough in a cold room is not.
Different Temperatures Top and Bottom
In a single-zone cabinet a small gradient is normal, and in a dual-zone cabinet a large one is the entire point. Cool air is denser and sits low. If your cabinet is dual-zone, check which zone the display is reporting before deciding it is wrong.
Not fine: a gradient that has grown over time, or one large enough that bottles at one end are outside the band. That usually points at the internal fan or at airflow blocked by the way the shelves are loaded.
The Display and the Thermometer Disagreeing
The display reports its sensor, and the sensor is in one place. A thermometer standing among the bottles reads the mass, and the mass lags. A few degrees of disagreement, especially shortly after loading or after the door was open, is the two instruments measuring different things.
Not fine: a persistent gap of several degrees that does not close after a day, or a display reading that does not respond at all to a setting change. Either is a sensor or control question and is worth measuring properly before anyone orders a part.
Noises
Expect a low hum from the compressor, a soft rush from the internal fan, and occasional ticking, gurgling or a faint trickle as refrigerant moves and as any defrost water runs to the drain. Expansion clicks from the interior as temperatures change are normal.
Not fine: a rattle that varies with the fan, a buzzing that is new, a hard knock when the compressor starts, or a cabinet that trips a breaker.
Vibration, Light and Door Habits
Two more that owners raise. A cabinet standing next to a washing machine transmits spin vibration into the bottles, and that is worth solving even though the cabinet is faultless. And the interior light is for looking, not for display: leaving it on adds heat and exposes the bottles to light, so a cabinet that seems to struggle in the evening may simply have its light on all evening.
If what you are seeing is on the second half of each pair above, move the bottles somewhere cool and stable and book a wine cabinet repair with the setting, a thermometer reading from inside and the ambient temperature of the room.