Looking at it mathematically, their feedback for the past month is 3.3% negative or neutral, and 5% neg or neutral for the past 7 days. I'll admit that someone is not going to get everything perfect, but I wonder if this person isn't just overwhelmed and can't handle everything.
Looking at it another way -- half of their negative or neutral feedback in the past month has happened in the past 7 days, while only 32% of their total feedback for the past month has been posted in the past 7 days.
(I missed my calling .... I should've been a statistician)
If I was considering buying from them, I would be reconsidering. If they were buying from me, I would be concerned. As for their feedback being private, it's a tough call. Maybe they're hiding something, maybe some of the feedback was unnecessarily vindictive. I honestly don't know why someone would make their feedback private.