“Obviously, because this is so new to Fall River, it’s very disappointing,” said Fall River Mayor Paul Coogan. “My hope is that going forward, they’re able to correct these mistakes and either put out a schedule they can comply with or not run the trains and tell people those trains are not available.”

Since its launch on March 24, service disruptions on the New Bedford/Fall River Line — a project that cost more than $1 billion between building new stations and tracks — have been reported daily, according to a review of posts on X from MBTA Commuter Rail Alerts, an official account.

A private contractor, Keolis, runs the agency’s commuter rail operations and maintenance.

Between Saturday and Sunday, a total of 18 trips — inbound and outbound — were replaced with shuttle buses due to a lack of staffing. Amid the troubles plaguing the new line, the MBTA said it is extending fare-free weekend service through May, which was previously set to expire at the end of April.

As of Wednesday, there are 54 qualified conductors on the South Coast Rail territory, according to the T. Keolis, whose contract is due to expire in mid-2027, is currently working to increase that number, with a plan to reach 65 on the line by early June.

Coogan said he was not aware the line was short-staffed “until these mistakes flared up.”

“Leaving people in Boston or telling people to take a four- or five-hour bus ride is pretty much my idea of nothing,” he said. “And I know the way the MBTA works. They know they have to correct it.”

Before the start of service, T general manager Phil Eng said in a statement that the agency directed Keolis to “develop a schedule that provides sufficient service to attract ridership” and the resource needs, including crews, to fulfill that schedule. “Prior to the announced opening, Keolis confirmed their readiness,” Eng said.

On weekdays, trains to and from South Station are scheduled to run every 70 minutes, and on weekends, every two hours. Weekday service has seen the more consistent service being delivered, Eng said.

“Like our riders, we are not pleased with the need to replace selected trains with buses on weekends, and we apologize for these disruptions,” said Eng, who noted the T has been in “constant communication” with Keolis.

As of Monday, Keolis had been fined $51,451 because of crew issues disrupting service, according to the T.

Earlier this month, Tanya Kieron, 54, was among a group of abandoned passengers.

Kieron, who lives in Warren, R.I., took the commuter rail on April 13 from Fall River into Boston with her partner to enjoy the afternoon together, and they intended on riding the 6 p.m. train back.

But when they arrived at South Station, the transit hub was brimming with commuters and the couple learned their trip had been canceled — at least the third on the line. A customer service agent suggested they take an 8 p.m. train to East Taunton, where a bus would be waiting to take them to Fall River, Kieron recalled.

Around 9:15 p.m., when about 75 riders, including young children and the elderly, exited the train into the rainy night, “there was nothing” at the station, Kieron said. Spotting an empty MBTA bus with its brake lights on, she pried open the doors. Some passengers sheltered inside, while others found alternative ways home.

Eventually, several confused employees with the transit agency arrived and advised those remaining to take the upcoming late-night train to Fall River. Kieron didn’t get home until well past midnight.

“You can’t strand people like that,” Kieron said. “We did need real service here on the South Coast. People who want to go to Red Sox games, Bruins games, Celtics games, people who have appointments ... maybe even for workers who don’t want to drive. But I think they’ve definitely failed in this.”

“It’s a failure,” she added. “It’s not even hiccups.”

With the Fall River line only about five minutes away, Christopher Kearns, 37, of Portsmouth, R.I., was looking forward to commuting to Boston on the train, where he works for the Teamsters Local 25 union.

“I was so excited for it,” he said. “I can take a little bit more time getting up and heading out to work.”

But the recent troubles, while not surprising, Kearns said, have discouraged him from trying. “I don’t want to be working eight or more hours a day, then have to wait on a train for it to not show up,” he said.

Still, Eng said he is “confident that we can, and will, turn this around.” The commuter rail system here has seen the strongest post-pandemic rebound of any of its peers in the country, he noted.

“Restoring passenger rail service to the South Coast is an accomplishment we are very proud of and we are not wavering on our commitment to deliver consistently reliable service that people can depend on,” Eng said.

Shannon Larson can be reached at shannon.larson@globe.com. Follow her @shannonlarson98.