[Motor31]

The high humidity switch won't keep the interior from frosting up, it just keeps frost from building up inside the door seal area. If there is an air leak the frost would travel towards it eventually building up ice in the doorway itself making the leak worse. The switch causes a small heat strip inside the doorway to melt any frost that might be building up there.

I think your best bet is to get another door seal and install it. I Don't recall off hand what the warranty period is for the fridge or if the seal is even covered under it. If you have the booklet for it you can check or go online with Dometic and check there.

FWIW on our fridge we have to defrost about every 3 weeks to a month in high humidity areas like the coast and about 2 months in the desert like Arizona. We do let it build up a bit before we defrost. At least it is a quick process.