Ollie Harris unzipped the door of the green tent he shares with his girlfriend of 25 years and took a step onto the grass at a homeless encampment near Lake Merritt in Oakland. Sweating from the heat, Harris grabbed a wooden chair and moved it under a small patch of shade.

As he settled into his seat, he couldn’t help but think, “I have to get out of here.”

Nearly a year ago, Harris and his girlfriend, Debra Lang, were given a spot in Oakland’s community cabin program — sites that offer emergency housing to homeless people in the form of sheds. They had been sleeping on the concrete outside the Oakland Museum for a year before advocates intervened and helped them move into a community cabin.

Harris, 69, and Lang, 63, lived in a cabin for a month before they were placed in an apartment in Stockton. In less than six months, they found themselves back on the streets of Oakland.

The case shows the complexities of managing Oakland’s growing homelessness crisis, which has exploded to at least 4,000 people living in encampments and scattered throughout the city. Oakland has sanctioned some camps where it provides services including portable toilets, and operates an expanding network of cabin sites, shelters and safe RV parking areas. Still, the magnitude of the problem — homelessness grew 47% from 2017 to 2019 — poses a huge challenge.

Harris and Lang were deemed a success by Oakland because they were placed in permanent housing — even though it was outside the Bay Area and it did not work out for them. The city says it can not track what happens to people after they move out of the community cabins. But advocates say the rate of homeless people transitioning successfully into long-term housing from Oakland’s cabin program is not as high as the city’s own numbers suggest.

Officials have said that the city’s community cabins program is a critical part of the emergency response to dealing with a rising population living on the streets. The city operates four cabin sites and is in the process of opening several more over the next few months, including one near Jack London Square by the fall.

Advocates agree that Oakland’s thinking-outside-of-the-box program to offer emergency housing could work, but argue that some aspects of it need to be amended. Each cabin houses two people and often, the two people are strangers, said Talya Husbands-Hankin, a member of Oakland’s homeless advocacy working group.

“We have been asking the city ... to house people in single spaces because we know that will be much more successful,” Husbands-Hankin said. “People are coming in from living in a tent by themselves to being crammed in a tiny space with a stranger. It’s not a realistic expectation for success.”

City officials say the program works — 340 people have gone through. Of those, 216 moved on to permanent or transitional housing, and 124 went back to the streets. But they acknowledge their tracking system is flawed.

“Do those people become homeless again? That is the big question that we want to know,” said Lara Tannenbaum, manager of the city’s community housing services. “Any program that houses people, there are some percentage of people that become homeless again. Our hope is that that is a really low percentage, of course.”

The city relies on a countywide program called Homeless Management Information System. The program can track how many people in Alameda County returned to homelessness after going through an assistance program. But it doesn’t track the data on an individual program basis.

“We recognize that it’s a problem and we are working to fix that,” Tannenbaum said.

The community cabins program was implemented in December 2017 — the idea inspired by similar models in Oregon and Washington, said Joe DeVries, an assistant to the city administrator’s office.

Since its implementation, officials from San Joaquin County, Santa Rosa and San Jose have toured the city’s facilities, DeVries said.

The cabins — Tuff Shed supplied the first batches but the city has found a new manufacturer — are made of drywall, are insulated and have double-pane windows. The sheds have one or two cots, a blanket, socks, hygiene items, lights, outlets and two storage bins for each occupant. Extra blankets are provided during winter months. Sites have portable toilets, washing stations and shower service. Operation costs are about $1.7 million per year and startup costs to build a new site are $1.3 million.

The city aims to move cabin residents into more stable housing within six months.

Moving people to surrounding cities, like Stockton and Sacramento, isn’t uncommon, Tannenbaum said. Case managers at community cabin sites are tasked with finding affordable, available housing anywhere. And if the person is OK with moving there, they move.

Harris and Lang were wary about moving to Stockton, but it was the first permanent housing option that was offered and they were desperate. Lang suffers from seizures, they needed a roof over their head, they need some kind of stability.

Stability for Harris, who lived in Oakland for more than 40 years, and Lang never materialized in Stockton.

“The first day we got there, I was upset because we laid down and roaches came out everywhere,” Harris said. “The very first day.”

Over the course of the next few weeks, there were multiple shootings in their neighborhood, including one homicide, Harris said. Soon after, Lang’s purse, containing a portion of their rent, was stolen. When the couple couldn’t make rent because they were about $200 short, Harris told the apartment managers they would leave.

“I gave my word and my word is who I am, so we left,” Harris said.

Advocates say Harris and Lang’s experience isn’t unique.

“People are ending up back on the streets with nothing and it’s up to advocates to support them,” Husbands-Hankin said. “I provided Ollie and Debbie with a tent. They had nothing. They were literally just sleeping on the cement next to the lake.”

Despite the criticisms, the program has worked for dozens of people, including Michael Williams. The 37-year-old lived at a community cabin for about five months before being placed in a single-room occupancy hotel. He works as a security guard and said the case managers at the community cabin sites helped others obtain their license.

“It was a very positive move working with my case worker,” Williams said. “It was very kind of her to get me in here.”

Harris and Lang say they may move back into a cabin if the city allows it. They are growing weary of new people moving into their encampment and starting fights, Harris said.

“We had to do what we had to do,” he said. “It is frustrating.”

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani