Just a thought... may not be the answer. But Sunday evenings are an especially busy time on eBay. Lots of people adding listings, lots of listings closing and lots of people browsing and bidding. I have been online since early evening to late morning adding listings and watching auctions, etc. and eBay has been running very slow. For a while there I was getting lots of errors while browsing because it was choking.
It may be that there just was not enough lead time on your snipes to get them there in time. Since I don't know what your lead times were and exactly when you snipes were supposed to run, I'm just guessing... but it's something to look into.
Hope that helps.
diva (aka Dag)