This kind of unit are lubricated with grase paste. If the unit stays
inactive for a long time, or if the motor and gears are overheating the
grease paste gets melted into thin oil, and that will cause leaks.
To lubricate the unit, you need to spread again the grease in the gearbox, using special
foodsafe grease paste.
Disassemblying the gear box is not that easy, you will need previous
experience and a gear puller to do the job properly and safely.
This appliances are also held with security screws to prevent the users
from taking apart the unit, and can only be disassembled using a Security screwdriver tip.
The grease can be purchased here, check at the bottom of the page: Kenwood chef food mixer Grease.