iv had my becko fridge rezzer for 14months but the frezzer is now defrostin?

hi iv had my becko fridge frezzeer for 14 months my fridge is working fine although is running quite now but my problem lies with the frezzer the passed 3 days is is defrosting the food its still cold but not enough to keep stuff frozen properly dose anyone know what this might be? please help thanx lucy x