I have had the above freezer for about 20 months and during that time the middle drawer use to stick when pulling out and pushing in,also the evaporator support would fall out,the freezer was always needing to be defrosted,I never called an engineer as I always though it was just a bit of rough handling by various people.After defrosting it again I decided to have a look round and took some measurements. With the door off I measured the top meddle and bottom and the results are Top 595mm Middle 600mm Bottom 595mm,could this be the problem,and would this affect the door the build up of ice more often than normal