Most everyone has heard, at one time or another, the old slogan attributed to the United States Postal Service: “Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds.”

These days, it seems, those appointed rounds are anything but swift, taking some carriers late into the gloom of night. And for an agency beset with financial woes and staffing shortages, the problems may not end there — in the Bay Area, evidence has grown in recent years of chronic problems with deliveries delayed not by hours but days, and mail dropped off at the wrong addresses by harried carriers rushing to complete marathon routes.

Postal union members and management concede that retention issues have led to short staffing and delivery challenges, though there are differing opinions about the extent of the problems and whether they’re temporary or more deeply rooted.

One thing that is clear, however, is late-night mail deliveries have become commonplace in many areas. Susan Wengraf, a member of the Berkeley City Council, said that about a month ago she started seeing her mail delivered around 10 p.m. or later.

“It seemed unusual, but at least I was getting mail,” Wengraf said.

Then she heard from neighbors and constituents whose mail was taking days longer to arrive than it should — or not showing up at all. “I suddenly realized … there are people who get medications by mail delivery, Social Security checks — people are dependent on mail for very important things.”

Oakland resident Terry McGlynn has also noticed that her mail often shows up late in the evening.

A postal worker told her that with not enough mail carriers, he sometimes had to start a whole new route when his shift was done, McGlynn said. “People of course want their mail, and it is also not safe to have workers out late at night in the dark and exhausted,” McGlynn said.

It’s an issue plaguing mail delivery around the Bay Area, with residents routinely reporting problems with late, mis-delivered or missing mail.

Sandra Dieffenderfer, a letter carrier in Burlingame and executive vice president of the Branch 1280 National Association of Letter Carriers union, has worked for the postal service for 29 years. She’s always been proud of the service, but she’s frustrated.

“We’ve never failed. We’ve always been really proud to get out the mail,” even during busy holiday seasons, she said. “But this year I see failure, and it’s sad.”

How to explain the current struggles for a service that was established before the U.S. Declaration of Independence was penned, and has long prided itself on reliability and promptness? A perfect storm of factors, it would seem.

With the long-term decline in the historical backbone of the postal service, First Class Mail, and improved technology that sorts mail automatically and frees up workers’ time, the agency has retooled its business model and decreased its workforce by not filling positions after workers left or retired.

It created broader routes that cover more ground but require fewer letter carriers, said Augustine Ruiz — a spokesman for the Bay Valley postal district that stretches from Napa and Fairfield in the north, over the East Bay and south to Big Sur and Santa Cruz — in an email.

But those changes have fallen short as the volume of the labor-intensive packaging business grows (the USPS recently partnered with online giant Amazon) and the agency has faced staffing shortages in the competitive Bay Area.

It has been a particular challenge this year, with the postal service swamped first by the flood of political mailers during the 2016 election and now by a holiday retail season in which online shipping has grown more popular than ever. The USPS shipping and packages business grew by $2.4 billion, or 15.8 percent, from fiscal year 2015 to fiscal year 2016.

The Bay Area in particular “really hit the perfect storm,” said Brian Renfroe, executive vice president of the National Association of Letter Carriers. “It being a very affluent area results in e-commerce and mail volume higher than the average area, then there was the election and political mail, and all that working together really increases the workload.”

From fiscal year 2014 to 2015, the postal service added 1 million delivery points to its network, according to a report from the USPS Office of Inspector General. That came after the USPS began to turn to part-time employees and adjust routes.

The postal service has been trying to fill its vacancies with city carrier assistants, entry-level employees who are tasked with delivering and collecting mail. The Bay Valley district has hired 305 city carrier assistants and 187 mail-processing clerks at its processing centers in Richmond, Oakland and San Jose since November. To meet demand in the holiday period, when mail volume increases, the district hired an extra 303 seasonal employees, Ruiz, the agency spokesman, said.

Bringing on additional carriers should help carriers finish with their routes and get back to the office by 6 p.m., Ruiz explained.

But retaining employees has been a problem. According to documents from a 2015 compliance review by the Postal Regulatory Commission, the average annual turnover rate for fiscal year 2015 for non-career employees was 38.7 percent. For city carrier assistants, the rate was 54.2 percent.

Renfroe said the NALC is working with postal service management to examine ways to retain employees, including adjusting training, benefits and compensation, which he acknowledged can be challenging in expensive areas like the Bay Area.

According to online job postings, wages for city carrier assistants in the Bay Area start at around $16 per hour.

“They can’t afford to live here on $16 an hour,” said Dieffenderfer, the Burlingame letter carrier. “They get hired, they pass probation and then apply for a transfer somewhere else.”

A lack of workers isn’t the only problem, Dieffenderfer says. Often, she said, broken trucks — part of a 25-year-old fleet of “long-life vehicles” — hold up routes, or scanning devices used to check and track packages are not working. With a high volume of packages and limited workforce, every minute counts, and hiccups like those are crushing.

The USPS has begun the process of acquiring a new fleet of vehicles, but with thousands of trucks to replace, the cost could top $6 billion — a sizable sum for an agency not exactly flush with cash.

The postal service, which does not receive tax dollars for its operating expenses but is exempt from paying federal taxes, posted a net loss of about $5.6 billion for fiscal year 2016 (ended September 2016), which follows its $5.1 billion net loss for the 2015 fiscal year. In a November news release, the postal service blamed the loss on a $5.8 billion obligation to pre-fund future retiree benefits.

U.S. Rep. Mark DeSaulnier, D-Concord, who represents California’s 11th district and serves on the House Committee for Oversight and Governmental Reform, which oversees the postal service, said various efforts are afoot at that level to reform the service. One, the Postal Service Reform Act of 2016, would restructure the way it invests in health benefits of its employees and attempt to restore the agency to financial solvency and improve its operations.

DeSaulnier said he has received many complaints and questions from his constituents about late or missing mail, and that both he and his constituents have struggled to connect with local postal service management.

“It has to be fixed.”