I have several accounts, and in fact one of my best sellers with highest volume is also one of my worst accounts in terms of neg. FB.
It's been my expereience that feedback doesn't matter that much, and is not really seen or viewed by most buyers, especially those using the moble app to check out in BIN listings.
To be fair, you just got the neutral last night so it's far too early to say that is the cause of your sales dropping off. More likely, it might be search placement. The Cassini algoritm that eBay uses takes a variety of factors into account. How are the other DSR's on the account? Any past issues, or defects?
Check your placement in search when you look for your item? Is it still on the first page, or got pushed back to the end?
Negative and neutral feedback 
