About 30 people were stuck on the ride when it was stopped at about 12.00 BST.
A spokeswoman said a piece of rubber "came away from one of the carriages." "At no time were any guests at risk," she added.
The ride reopened in March, nine months after the horror crash.
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In a statement, the theme park said all visitors were evacuated from the ride in 30 minutes.
"The ride remained closed for a short period to investigate the matter, which is part of our standard process in assessing minor incidents," it added.
"The technical team have declared the ride safe and The Smiler re-opened at 16.22."
Liam Dennett, 33, from Cheltenham, was in the queue for the ride when an announcement was made about a "technical fault".
He said: "The ride's still closed now. We can see it in the distance that it's still closed. I would say between 30 and probably 35-40 minutes that they were stuck for."
He said he would not go on the ride after seeing what happened.
"My son still wants to go on it, but I wouldn't go on it personally now," he said.
Two women needed amputations after two carriages crashed on the track in June 2015.
Merlin Attractions Operations Ltd admitted breaching the Health and Safety Act after an investigation found the crash was caused by human error.
The Smiler rollercoaster at Alton Towers had to be closed after debris fell from a carriage - 14 months after it crashed leaving five people seriously injured.