Frank Paytas was getting dressed to go to his job as a mechanic when Prince George's County sheriff's deputies knocked on his door at 4:45 a.m. last week. The deputies held a warrant for Paytas' arrest, issued because he had failed to keep up his child-support payments.

Paytas, 39, had brought his payments up to date more than three months earlier, but the county Office of Child Support Enforcement had not notified the sheriff's office, and the warrant was still out.

Paytas said he tried to explain to the deputies that he had documents to prove the debt had been paid, "but they told me that everybody says that." He was taken away in handcuffs, wearing what he happened to have on at the time, a pair of white athletic socks and gym shorts. It was 30 degrees outside.

Later that day, after Paytas told his story to Domestic Relations Master Clifton Grandy in court in Upper Marlboro, his case was closed and he was released from custody.

By then, Paytas, of 5297 85th Ave., New Carrollton, had spent seven hours in custody.

"The [child-support] collection system is so screwed-up," he said bitterly.

Paytas was one of 72 persons, including 10 women, arrested last Wednesday during a roundup of parents who are delinquent in their child-support payments. Cases such as Paytas' are not the norm, but critics of the early-morning sweeps said his story illustrates the pitfalls of such operations.

"Joint custody is the best way to ensure that parents pay child support because when the parents are around, so are their wallets," said David L. Levy, president of the National Council for Children's Rights, who compares the roundups to "KGB-type midnight arrests."

Paytas' mistaken arrest was the result of a backlog in casework in the Prince George's Office of Child Support Enforcement, said Meg Sollenberger, the office's executive director. The current office was formed in July with the merger of the Circuit Court's Support Collection Unit and the State's Attorney's Child Support Division.

When the two units merged, there was a 50 percent turnover among caseworkers, Sollenberger said. And now only 21 of 24 caseworker positions are filled.

Some of the custodial parents are skeptical about the enforcement system, saying noncustodial parents have learned to get around the system.

Wilhemenia Dorsey, 40, whose former husband, Ernest Leon Dorsey Sr., 41, was one of the 72 persons picked up last week by the sheriff, credits the county for "taking aggressive steps to collect child support." But she said that in her case, the benefits are only short-term.

According to court records, Wilhemenia Dorsey, who lives in Upper Marlboro, first filed a complaint against her former husband for nonpayment of child support in June 1982, when he was more than $1,400 in arrears. By December 1982, when the county took over collection of Ernest Dorsey Sr.'s payments, he was $2,600 behind, according to court records. The Dorsey teen-agers are now 19, 16 and 15, and Ernest Dorsey Sr. is obligated to help support the younger two.

The support collection unit requested that a warrant be issued for his arrest in April 1983, court papers said, when his payments were $4,025 in arrears. He turned himself in to the court in August 1983 and was released on his own recognizance when he promised to pay $1,500 within 30 days.

He made that payment on time, but two years later was behind again, this time for about $9,000 in support, according to court records. The warrant that led to his arrest last week on contempt of court charges was issued after he missed a court hearing in October.

"The system is begging [noncustodial parents] to do right -- and that's about it," Wilhemenia Dorsey said. She predicted that as a result of last week's court action, her ex-husband "might make payments for about three months."

"It hurts, it hurts, it hurts," she said of her ex-husband's failure to keep up support payments for their children. "I'm talking about day-to-day things, like lunch money for the kids. I'm not talking about $60 tennis shoes."

Ernest Dorsey Sr., who lives on Arnold Road in Suitland, told Court Master Grandy that he hadn't missed a payment for six years until a streak of bad luck forced him and his brother to close their small contracting business. He is now unemployed, he told Grandy.

"All of a sudden when I'm broken," he said, "everybody comes down on me. I just try hard, that's all."

Grandy asked Ernest Dorsey Sr. whether his new wife would consent to having part of his payments deducted from her salary. She agreed, and he was released.

"The past three years have been difficult," Ernest Dorsey Sr. said in an interview. "It has been rough. Nobody seems to understand. When I'm employed, they get their money. When I'm not, it's harder for me to make payments. I love my children. When I could afford it, my kids were going around with $70 jackets. When I got broke, everything changed.

"The county makes it look ugly," he continued. "This is a civil matter, and I'm being treated like a criminal. It takes away your dignity."

Levy, of the Council for Children's Rights, said that wage assignment, which was the outcome in a majority of the cases in last week's sweep, isn't always the answer. "It's not going to work for the unemployed or the job-hopper," he said.

That happened in the case of Charmaine Barkley, 36, who lives in Southeast Washington and collects support through the agency in Prince George's, where the father of her 15-year-old son lives. At a court hearing last December, the man was ordered to pay by the middle of January half of the $3,000 he owed in back payments. He paid $450 and agreed to a salary deduction, according to court records.

"He changed jobs after about four months," and hasn't sent any support money since, she said.

"What good does rounding them up do?" she asked. "The court doesn't have any way of enforcing anything they do. By the time they get them back in court, a year has gone by. The county is making an honest effort, but it's not doing me any good."

Said Levy: "That's why we favor joint custody. The kids would benefit the most from it."