KNOCK ON WOOD! I have never had a no-send or a no-pay. I have had a few slow-pays, but very few. Had a no-arrival and the guy sent another chip, I thought was more than fair as I took the risk by no ins on the package.
I like Jackpot for chips as there is seldom a no-bid close. On ebay the market is not so specialized as Jackpot. Downside is profit is better on ebay, that may be the difference in auctions. JackPot you see mostly other CCGTCC members. I cut a LOT of slack when I see that. Haven't been burned yet, but it will happen sooner or later. Then I'll tighten up. Sorry you have had a bad experience, that wipes out a LOT of good ones.