Hotpoint fridge freezer modelNo FFUQ1810/P?

Hotpoint fridge freezer model No FFUQ1810/P
Serial No34744300100 Age 8 years
Twice maybe 3 times in its lifetime it has suddenly decided to defrost completely with total loss off the contents. It is then cleaned and restarted it will then work perfectly until the next time say in 12 months. There is no obvious reason for this, as in say loss of the power supply or alteration in the temperature. Help or ideas needed please as Hotpoint have been unable to offer any sensible advice. Many Thanks