Doorbell Lens peeling/ blurred

My doorbell lens suddenly looked cracked but on closer inspection it’s like a thin layer of plastic peeling off and obscuring the lens so I get a hazy area and it’s just as someone approaches the door I wouldn’t be able to view them clearly. I’ve had the doorbell a while but in UK I wouldn’t expect this to happen, I’ve seen similar in hot country’s where this has happened is the lens covered as a spare part or fixable.