The BHA has apologised to punters after stewards at Chester misinterpreted the rules and incorrectly revised the placings of the 1m3½f handicap (6.55) won by Infrastructure last Friday.
The stewards deemed that Dark Red, who was second past the post, had improved his position by hampering Lunar Jet, who dead-heated for third with Vivid Diamond.
They promoted Lunar Jet to second, demoted Dark Red to third and placed Vivid Diamond fourth.
However, the rules do not permit horses who have dead-heated to be split, unless there has been interference between them.
Lunar Jet and Vivid Diamond should have been treated as a single entity, so had the rules been interpreted correctly Dark Red would have been demoted behind both horses and placed fourth.
After investigating the matter over the weekend, the BHA revised the result to place Dark Red fourth behind Lunar Jet and Vivid Diamond, who dead-heated for second.
A BHA statement on Monday read: "The BHA understands the impact this will have had on a limited number of bets and that some disruption may have been caused to both off and on-course operators and their customers, and apologises for this.
"It will now consider what steps to take in the future to minimise the risk of such an incident reoccurring, which may include publishing specific guidance relating to interference involving horses who have dead-heated."