I have an E521T. It was beeping so we pulled the back of the freezer compartment off and there was an enormous amount of ice build up and the front coil had dropped down. We got rid of all the ice and replaced the fan unit. It still beeps and the light flashes. We push the mode button and it stops beeping for a few hours but the light still flashes.

SOURCE: Drain plugged in freezer

First of all, is it ice or frost? If it is ice, I would say you have a leaky water valve to icemaker, running down evap. coils. Replace water valve. If you have frost-find out why it is not defrosting(defrost heater, defrost thermostat, or defrost timer.

SOURCE: Fisher & Paykel active smart E521T

I would reset the module. Open the fridge door, keep the freezer door closed, then press the mode button (located on the display panel. This will re initiate the electronics

SOURCE: E521T

close freezer door, open fridge door and press the mode button

SOURCE: Ice build up on bottom of freezer

remove back panel inside freezer. you will see drain tray at bottom with a drain hole in the middle - this is blocked usually with ice. melt off with a hairdryer and follow up with hot water till water flows away freely

SOURCE: ice keeps building up on coils

We had the same problem with our GE frig, a Profile 24. When the tech came out, he explained that the energy efficient models have only 1 defrost heater, but the older units had 2 and the hook up and mounting positions were still there. As long as I directed him to install the 2nd heater he could do it. It turned out the original heater was just fine, so the replacement was installed in the 2nd heater space and it has worked fine for several years now. Before doing this on yours, I would verify that the defrost timer is working and the heater unit is ok.