This is an ongoing problem, and I am sure it is me. We started with a cab over camper, went to a 5er, and now have a 29' Type B+. All were new when we bought them. In each case, I have had to defrost...
We have used our travel trailer and our class C for months (1 - 4) at a time and not needed to defrost. Friends of ours have had issues...so I am curious.