DIAGNOSIS: Random beeping is almost always a button on the control panel (either the physical buttons on the unit or the touch buttons) being triggered by a fault. This can be caused by moisture, conductive dust buildup behind the panel, or a failing tactile switch.
FIX: Unplug the fan. Wipe down the entire control panel area with a dry microfiber cloth, paying special attention to the seams around the buttons. Then, use a can of compressed air and blow around the edges of every button to dislodge any conductive dust or debris that might be causing a short. Let it sit unplugged for an hour in case any residual moisture is present. Plug it back in and see if the phantom beeping stops.
IF THAT DIDN'T WORK: If the beeping persists, a specific button membrane or the main control board is likely faulty and registering false presses. You can sometimes isolate it by gently pressing each button multiple times to see if one feels "sticky" or different, but the fix usually involves board replacement.
HEADS UP: Avoid using cleaning sprays or liquids near the control panel. If it's in a humid room like a bathroom or kitchen, that environment can accelerate this problem. A dehumidifier nearby might help prevent a recurrence.