Every time David Waxler drives by Shalom Memorial Park, he can't shake the sense that he failed his mother, Edna, in the days after her death.

"I feel personally that I didn't do a good job," said Waxler, 68, vice president of finance at a small pharmaceutical manufacturing firm. "I felt like I did her a disservice, because I couldn't get her into her final resting place when she should have been here."

Edna Waxler died last June at the age of 99. She was supposed to be buried two days later – as soon as possible, as Jewish custom requires – next to her husband, George, 93, who died in 2014.

But on the morning of her funeral, David Waxler said, staffers at the cemetery in Huntingdon Valley discovered the remains of someone else -- identity unknown -- in the plot bought for his mother.

"The funeral parlor said they've never heard anything like this before," Waxler said last week, while standing by his parents' grave. "We went through the whole ceremony, then the funeral parlor took her back and put her back in the refrigerator, which is unbelievable."

The cemetery, run by Houston-based Service Corporation International, which describes itself as North America's largest provider of funeral and cemetery services, gave Waxler some options.

It offered to dig up Waxler's father and move his parents to another location – and to give Waxler and his sister two free graves there – or to put his mother in a mausoleum.

"That's totally against Jewish law," Waxler said of both options.

The cemetery eventually agreed to clear out the grave so Edna and George Waxler could be buried there together, but SCI's Pennsylvania subsidiary first had to obtain a court order in Montgomery County to remove the unidentified remains and rebury them elsewhere.

Edna Waxler wasn't buried until July 31, more than a month after she died.

"When you think of the turmoil that the body has to go through to come here, and then not get into the grave," Waxler said.

Waxler and his sister are now suing SCI in Philadelphia Common Pleas Court, alleging that SCI continues to "perform new burials in areas which are saturated with existing graves," leading to the "discovery of unidentified corpses in pre-purchased grave-plots."

This isn't the first time SCI has been sued for these types of problems at one of its approximately 2,000 cemeteries and funeral homes – or even the first time at Shalom Memorial Park, where Sen. Arlen Specter is buried.

The Daily News reported in 2014 that other families had similar trouble  at Shalom, including Maya Devinskaya, 73, whose 42-year-old daughter died in 2013. Devinskaya sued SCI after her daughter was buried in a plot that overlapped someone else's. That case was later resolved on confidential terms.

Another woman told the Daily News that cemetery staff called before her mother's 2010 funeral and said that there was no room in the prepaid plot.

"It was ridiculous," Susan Helfand said. "People are telling me the limo is waiting, and I'm talking to Shalom trying to figure out how they are going to bury my mother. It was indescribable."

SCI, a publicly traded company with 24,000 employees, generates about $3 billion a year in revenue. It has paid out several eight-figure settlements, including $80 million in California in 2014 to settle a class-action suit alleging that staffers at an SCI-owned Jewish cemetery had repeatedly mishandled human remains and desecrated graves.

But the lawsuits don't seem to have forced the company to change.

Attorney Bryan Lentz, who is representing Waxler, described the situation as a "nightmare" and said: "You should only have to have this happen one time before you do a complete inventory." The company also has been disciplined by Massachusetts authorities for digging up bodies and reburying them without promptly telling their families.

SCI would not comment on its burial policies, instead releasing a two-sentence statement Friday in response to questions from the Inquirer and Daily News: "Shalom Memorial Park is committed to honoring its commitments with families. Because these matters are the subject of litigation, we cannot disclose further details."

Joshua Slocum of the Funeral Consumers Alliance, a consumer-rights group, said SCI appears to have acquired cemeteries without a full knowledge of how many bodies are in the ground, and where.

"Whose responsibility is it to do the due diligence before the sale?" Slocum asked. "One assumes not only the profit potential but the liability potential. A company can't say: 'We didn't know. We just bought up all these cemeteries.' That's the problem. You bought all these cemeteries without checking to see what was going on with them because you didn't really care."

University of Louisville archaeologist Philip DiBlasi, who works with Kentucky law enforcement authorities on cemetery overcrowding cases, said "double burials" often arise when a company like SCI buys a cemetery and doesn't retain the institutional memory of the previous owner.

"That's happening more and more since SCI has been buying up cemeteries," DiBlasi said, referring to cases like Waxler's.

DiBlasi said SCI could use probes to determine if graves are empty or occupied, but it's a time-consuming process. Still, he said, "that's the kind of thing that needs to be done when these older cemeteries get taken over."

Cemetery regulation is particularly lax in Pennsylvania, so complaints about overcrowding and desecration are often resolved through private lawsuits. SCI owns 10 funeral homes and cemeteries in the Philadelphia area.

"We very often get calls about problem cemeteries and there's not one agency that oversees every aspect of a cemetery," said Wanda Murren, spokeswoman for the Pennsylvania Department of State. "There is not one agency that can really step in and make a cemetery do all that it's supposed to do."

Slocum said states like Pennsylvania need to enact strict regulations.

Two months after Waxler held the "second funeral" for his mother – when she was actually buried – his mother-in-law died and was to be buried at Roosevelt Memorial Park, also owned by SCI. But another casket was buried so close to his mother-in-law's prepaid plot that Waxler said he had to change caskets at the last minute so it would fit.

A short walk from the Waxlers' gravesite last week, fresh tractor marks ran directly over rows of flat headstones, some caked with so much mud that they were illegible.

Before he left, Waxler pondered where he would be buried.

"I'm not sure where I want to go pick up my plots," he said. "Find someplace they don't own."