I have not sold anything for several months on my selling ID, but I *think* eBay got rid of the option to block buyers with less than x amount feedback

(I'm sure a member who is active at selling these days can answer that better)

Having said that, if all five were all 0 feedback members, it is possible it was the same person more than once under different user IDs

I hope you reported them for non payment and added them to your blocked bidders list?

Was there a buyer at some point in the past who you had big problems from? (if so it is possible it is them, opening different IDs just to be a smart *you know what*)