One race had to be halted dramatically because the starting stands could not be removed from the track.
It became clear there was a problem when officials attempted to flag the pitch approaching the home turn at Chelmsford on Saturday.
Nine riders and riders were traveling at more than 35 mph but had to stop abruptly to avoid the pits, still on the track entering the final straight.
All horses and jockeys were unhurt and the race was canceled.
Jane Chapple-Hyam, who trained runner Salamanca, told the Racing Post: “When they load the horses into the stalls they turn off the tractor and I believe when the horses were jumping the tractor wasn’t shifting, so they couldn’t get him off the track.
“They didn’t have enough time to send the flaggers down the stretch. It was pretty scary.”
Jockey Alistair Rawlinson, who was on board Penzance, felt all riders involved deserved credit for stopping safely and avoiding any accidents.
“We were seated second so were among the first to arrive at the scene. It could have been a disaster,” he said.
“The guys showed great horsemanship to stop in a short period of time as we are about to kick into high gear.”
A statement from the racecourse said: “The safety of our participants is and always will be our top priority.
“We are deeply relieved that none of the jockeys, horses or staff involved were injured. Tonight’s incident is unprecedented in Chelmsford’s 10 years of racing and although the racecourse is not directly responsible for what happened, we fully recognize our role as the racecourse organizing the match.
“We are committed to working with the British Horseracing Authority (BHA) and our partners to carry out a thorough investigation and ensure events of this nature do not happen again.
“Forms of refunds will be arranged for affected connections and they will be contacted for further information.”
A report from the stewards said: “An investigation was carried out into the display of the stop flag in the closing stages of this race as the stalls could not be removed from the course.
“Present at the inquest were the racing director, clerk of the course and trainee racing director, both starters, jockeys Billy Loughnane and Harry Davies, the pit crew chief and the tractor driver.
“As all runners had stopped and the judge was unable to declare a result, the race was declared void and a report was forwarded to BHA Head Office.”
