Arrived at location on 8/17/22 - fan noise inside of the walk in freezer. At first glance noticed that cupcake containers were too close to the supply and return inside the walk in. Gained access to condensing/evap at top of walk in box and found heavy ice build up at expansion valve and fan. Using hot water, removed all ice and started unit back up. Monitored pressures and they were good for 404 refrigerant. Checked superheat at 5 degrees, and it was good around 12 degrees. Instructed staff to make sure they do not block the supply and return air grills inside walk in. Freezer is working properly at this time.