It depends on the domain name. So not getting domains you won are probably due to the original owner renewing the domain name if it was an expired auction. Usually if the domain is a GoDaddy registered domain name that expired you will get the domain at the end of the auction if there is 5 or less days in the auction to go. At that point it is normally too late to renew the domain barring some error or rare issue.
On domains that expired outside of GoDaddy there is a larger window to renew. I cannot go into it all because of NDAs with the sellers. Suffice it to say they can be renewed even after you pay in some cases. However the overall rate of that happening is very low. The poll results so far and the person saying they only have it happen about 1/2% of the time bear that out.
On names being listed for sale by someone else it seems like you are buying domains someone already owned. That unfortunately is the nature of the beast. Many times when you buy a domain name someone other than you already had it listed for sale. We are working on ways to continue to improve this. It isn't as easy as it sounds. The person who listed the domain proved it was theirs at the time they listed it and we don't always know it changed hands.
Last week I bought a domain myself at another company auction not in any way related to GoDaddy. I told one of my friends and they said why are you listing your name at Dan if you work at GoDaddy and Afternic
I do have names listed all over the place on purpose but this name was not listed by me at Dan and I still haven't reached out to Dan to straighten it out. Dan has a good system of verification. I know how to fix it. I am a busy person (and lazy sometimes on my own portfolio, after dealing with domains all day for 10 hours for other people I dont always want to stay at the computer and fix my own domains)
As a result the name I bought is listed at Dan by someone other than me. I am sure Dan did nothing wrong, the previous owner didnt remove the listing when it sold and I havent contacted them about it yet. It is just kind of how things work when you are buying domains other investors held at some point.
We are working to make it better. The auctions and Afternic are working on ways this year to continue to refine this and make it better. The old owner should take responsibility for removing the domain when they sell it and I should as the new owner be responsible and update the status for the domain I own. The platforms should also make this easier and better and involve less friction.