When New York legalized recreational marijuana two years ago, it was meant to tear up the path to prison that being convicted of possession had long paved.

But even as legalization took effect and New Yorkers could smoke with impunity, Frederick Volkman was sent to a maximum-security prison after violating the terms of his probation on a 2019 felony marijuana charge. Locked up with violent criminals, he did his best to avoid confrontations.

“I saw people out in the yard getting cut — there was a fight almost every day,” Mr. Volkman, 26, recalled in a phone interview from prison. He said there had been several suicide attempts: “I saw one person get pulled out of their cell on a stretcher.”

Thanks to the 2021 law, Mr. Volkman, who is to be released on Monday from a boot camp-style lockup, is one of the few remaining prisoners in New York incarcerated solely because of marijuana charges, officials said.

He will return to a world where marijuana seems to be everywhere, sold from storefronts and vending trucks, its aroma wafting on the street and from moving cars. But as many New Yorkers light up freely, complications created by the law linger, including thousands of uncleared felony charges that recall the state’s earlier, draconian approach to prosecution.

Legalization offered offenders a clean slate by wiping convictions from their records, a crucial step toward turning their lives around by making it easier to apply for a job or loan, rent an apartment or obtain a professional license. Expungement was a pillar of the law’s promise to reverse the consequences of the war on drugs.

The 2021 law expunged 107,633 convictions, and a 2019 law that decriminalized small amounts of marijuana cleared 202,189 more, state justice officials said.

Those convictions were largely for lower-level offenses. The situation is more fraught for people like Mr. Volkman who have felony convictions for large quantities of cannabis.

The vast majority of the nearly 9,000 felony marijuana convictions remain on offenders’ records long after they have served their sentences. In addition, scores of minor marijuana convictions that accompanied more serious crimes cannot be expunged automatically despite the law requiring it.

Most felons have not even sought to clear their charges — some because they did not know the new law allowed it, others because they thought it would happen automatically and still others because of the arduous filing process, advocates say.

Furthermore, the omission of a single digit in the legalization legislation — the Roman numeral i — has precluded felons from filing a straightforward form to receive a conviction reduction. The mistake remains uncorrected.

“It’s literally a typo,” Emma Goodman, a Legal Aid Society staff attorney, said of the error, which has prompted eye-rolling jokes about government dysfunction.

“Everyone in Albany understands it’s just a mistake, and there’s not an easy way to fix it,” she added.

The upshot is that instead of filing the form, felons seeking conviction reductions must have a legal motion drafted and submitted in the county court where they were convicted. The district attorney’s office that prosecuted the original crime can weigh in before the motion goes before the judge who imposed the conviction.

Such motions have largely sailed through in more liberal counties, like the five boroughs of New York City. But elsewhere, some are being opposed, a development that advocates described as troubling.

“There are still significant contingents in parts of the state that are opposed to the law and do not want it implemented,” said Ms. Goodman, who specializes in getting criminal records expunged.

A judge in Dutchess County, north of New York City, rejected one man’s motion to clear his record of a felony marijuana conviction. In a move that will most likely set precedent for similar challenges, the man is appealing the ruling.

A judge in Nassau County, on Long Island, issued a similar decision against a man who was seeking to wipe away felony charges for possessing 10 pounds of marijuana.

And after an upstate district attorney opposed a man’s motion in another case, it was denied by a judge, the man’s lawyer, Jeffrey Hoffman, said.

“My client has been denied employment advancement in his career due to a 20-year-old felony,” Mr. Hoffman said.

Although advocates are aware of only a few cases of felony clearance motions being opposed, the current ones are “the tip of the iceberg, given the many thousands of such convictions” he said.

Not everyone is eager for automatic forgiveness.

“We’d like to see a clean slate for lower-level convictions, but when it comes to high-level felony convictions, we need to go a little slower,” said Kevin Sabet, the chief executive of Smart Approaches to Marijuana, a group that opposed the legalization law before it passed and argues for what it calls sensible guidelines.

“People who might have been part of transnational criminal organizations, we wouldn’t want a computer determining what happens to their record,” Mr. Sabet said. “We’d want a judge to look at all factors and the whole context of the case.”

In the Dutchess County case, the judge did review the motion filed by Michael Graubard, 55, who was arrested in 2014 and charged with a felony for having 114 pounds of marijuana in his car.

Mr. Graubard pleaded guilty and served nearly two years in prison. He says the felony is the lone blemish on his record and has kept him from achieving his goal of becoming a schoolteacher, blocked him from getting other jobs and deterred him from applying for a home-equity loan.

“There is less of a stigma for cannabis now, but some people still won’t hire felons, even while the state is setting up a whole cannabis industry,” said Mr. Graubard, who has filed a motion to have his felony vacated.

Because the 2021 law still makes the possession of large quantities of marijuana a crime, including Mr. Graubard’s felony offense of transporting 114 pounds, William Grady, Dutchess County’s district attorney, opposed Mr. Graubard’s motion to have his record wiped clean.

The judge agreed and merely downgraded the conviction to a lesser felony. Mr. Graubard is appealing the decision. His lawyer, Wei Hu, argued before a four-judge appellate panel last month that the “statutory defect”— the typo — in the 2021 law should not affect his client.

Mr. Hu maintained that the judge’s decision to reduce Mr. Graubard’s conviction to a lesser felony was contrary to the 2021 law because it did not keep Mr. Graubard from suffering “severe and ongoing consequences.”

Anna Diehn, a Dutchess County prosecutor, noted that the large amount of marijuana Mr. Graubard had been convicted of possessing was still a felony under the new law and that the county judge had applied the statute correctly and fairly in reducing the conviction to a lesser felony instead of clearing it altogether.

A coalition of public defenders and advocates have been urging legislators to have the typo in the law amended, Ms. Goodman of Legal Aid said, but had been told that doing so would require introducing a corrective bill, which has not happened yet.

A spokesman for Crystal D. Peoples-Stokes, the State Assembly’s Democratic majority leader and a sponsor of the 2021 legislation, said her office was reviewing the issue and would make any necessary changes.

“It may take a little bit of time, but we’re on it,” the spokesman, Mark J. Boyd, said.

As for Mr. Volkman, who state records indicate is one of just two remaining marijuana-only offenders in prison, he filed a motion after the 2021 law passed to have his conviction vacated. A judge denied it.

In the phone interview, he said it felt incongruous to still be imprisoned for cannabis after it had been legalized.

“Marijuana is not a very dangerous drug — it’s not something that people should be badly punished for, especially with everything going on in New York and legalization,” he said.

He was arrested in 2019 at 22 with seven pounds of marijuana and $65,000 at his home in Glens Falls.

Under a plea agreement, Mr. Volkman, who goes by Derick, served five months in county jail but then violated his probation by failing drug tests for marijuana, which he said he had smoked since he was 13 to settle his mood and anxiety.

After being arrested for driving under the influence, he found himself resentenced on his original cannabis charges even as the state was pledging to give priority to marijuana offenders in awarding dispensary licenses.

Mr. Volkman said he hoped to eventually work in the legal cannabis industry and hoped that his drug charge would not hobble him professionally.

“If none of this was becoming legal, we wouldn’t be having this conversation,” his father, Fred Volkman, said. “But the fact that all this was evolving, with legalization, about how pot is now OK, people are saying, ‘It’s OK, it’s OK now.’ And they’re still pounding him. That’s the frustrating part.”