All 5 cancellations were initiated by me, because the buyer would not do so, nor would they pay.  All 5 were processed as "I have not received payment and wish to cancel an item" at least 3 weeks after the purchase was made, after waiting out the unpaid item dispute resolution.  They were also initiated by me in order to get the seller fees refunded.

First of all I agree the new defect system is flawed and certainly not an improvement on the old one, however in your specific situation I can't see that this is really eBay's mistake.  If you had followed the Unpaid Item Dispute procedure they would not have shown up as cancellations but NPBs. You don't get cancellation defects for NPBs.   Or did you bypass the dispute process and just cancel?  The only safe options with cancellations are "buyer wants to cancel" and "problem with address".  If you choose anything else eBay assumes you cancelled without the buyer requesting it and that means "out of stock".   If they don't pay you should always follow the UID process, otherwise how is eBay to know that the buyers didn't pay? I know eBay professes to know how buyers think and what they want, but really, they are not mindreaders.  I'm no "expert" but I would have thought with so much experience as a seller you would have to know the proper procedures?