Moulinex Masterchef 500 Classic Manual __full__
The lid tab is likely cracked. This is the only common irreparable part. You need a replacement lid (eBay is your friend). The manual has a diagram with the part number (usually 707006 or similar).
Is the Masterchef 500 Classic still competitive? According to the manual’s specs: Moulinex Masterchef 500 Classic Manual
