ice building up in freezer

This issue is confounding me! Ice is building up on the front cover of the icemaker and down into the ice chute out the door. I’ve replaced the inlet valve (no help); tried a known good icemaker (no help); tested the water pressure (all strong).

Currently, the icemaker switch is off. Water is off at the wall (and there’s no leak through the shutoff valve). Water is drained. But, as you see in the attached photo, I’m still getting ice buildup.

I’ve considered that perhaps the seal wasn’t good at the top of the door and so I was getting condensation which would freeze as it flowed downwards. But, to me, the seal looks good. And, I lowered the temperature which I thought would at least show a different freezing pattern if condensation were the culprit. So, I’m ruling this out unless someone convinces me otherwise.

Have you seen this sort of issue before?

Have you checked the ice chute door? If they don’t shut tight frost will build up in that area.

http://www.appliancepartspros.com/whirlpool-ice-door-assy-wp2180353-ap6005973.html