I held an auction and I had one player who had the winning bid for ALL of the horses. However, 3 of the horses did not go to them even though they had the higher bid. I looked at their barn space and there was room for them so unless it was an ebs issue (which these were CHEAP horses) it may be a bug.

I have screen shots just incase..

The Auction https://lensdump.com/i/tV3wJr

The stable with "room" https://lensdump.com/i/tV3cYb

And the 3 horses in their "other" homes

Hmmm regardless of ebs their account will still be deducted and go negative. They may not have had room when the auction ended perhaps? And made space afterwards