That has been my experience too. It used to be I'd get an automated response that indicated they never even read what I sent. Then for the past few years they would always give me full or partial credit. Then I went a long time without having to contest one. Last month I had two in a row that went all the way to the end and "sorry" - and their response was I must have gone too fast, blah blah blah and no reward.

I see a discussion here about getting suspended. That used to happen to me all the time when they would ask for comments after a survey...but they would always reinstate me. It seemed to only happen when i was $5 short of a reward :-0