Rarely in Olympic history had a single company been as ubiquitous as LVMH Moët Hennessy Louis Vuitton, the luxury goods empire owned by France’s richest family.

As the Paris Olympics’ biggest corporate sponsor, LVMH was everywhere. Its Moët & Chandon champagne flowed in V.I.P. suites. French athletes were clothed by LVMH’s Berluti fashion house. And, in contravention of at least the spirit of the Olympic charter, Louis Vuitton luggage was trotted out during the opening ceremony and seen by more than one billion people worldwide.

But its most significant role involved the Olympic medals, which were designed by Chaumet, a luxury jewelry and watch maker and part of the LVMH group. Gold, silver and bronze — the very best athletes would take them back home as mementos of their feats at the Paris Games.

Now those medals are falling apart — and LVMH has fallen silent.

In just over 100 days since the Olympics closed, more than 100 athletes have asked for their crumbling medals to be replaced. Last month, Clement Secchi and Yohann Ndoye-Brouard, French swimmers, showed their flaking medals on social media. “Crocodile skin,” Mr. Secchi wrote.

Nick Itkin, a U.S. Olympic foil fencer, said his bronze medal started to deteriorate a few days after the Olympics. “But after like a few weeks, it got more noticeable,” he said, adding that he planned to ask for a replacement.

Medals have had to be replaced in other Olympics — notably in Rio de Janeiro in 2016. But in no previous Olympics has a company stamped its brand credentials so prominently.

The issue seems to be most acute with the bronze medals, problems for which athletes first started flagging shortly after receiving them.

The International Olympic Committee has apologized and says it will find replacements. Monnaie de Paris, the French mint, which produced the medals, has so far taken responsibility, blaming the problem on a technical issue related to varnish.

And LVMH has been happy to let the other organizations do the talking. A spokesman for the company said because it did not make the medals and is not responsible for them, LVMH has no comment.

But in the buildup to the Games, and during the event itself, LVMH was showing off the roles of its expert artisans in crafting the medals. On the second floor of a club it created, just a few yards from the Élysée Palace, the residence of the French president, designers from Chaumet proudly explained the yearlong project to design the medals in secrecy. At the heart of each was a piece of the Eiffel Tower.

Chaumet had never previously designed a sporting medal, and of the three they were asked to make, the bronze was the trickiest.

“It’s the most difficult because it’s the most delicate,” Philippe Bergamini, one of Chaumet’s longest serving jewelry designers, told The New York Times at the time.

The company tweaked the designs hundreds of times until a special committee of athletes and Olympic officials were in agreement. Designers then joined forces with the mint, a French institution that has produced money and other precious objects since the Middle Ages.

Each medal took 15 days to complete, from stamping out the design to dipping it in gold, bronze and silver and then finishing it with a coat of varnish.

So when one athlete posted photos of his bronze medal rusting last August, just weeks after the Games, the mint began an internal inquiry to “understand the circumstances and cause of the damage,” the organization said in a statement.

The mint discovered that the varnish used to prevent oxidation was defective. Its varnish recipe is a trade secret, but the coating was weakened after the mint changed it to conform to recent European Union regulations banning the use of chromium trioxide, a toxic chemical used to prevent metal from rusting, according to La Lettre, a French industry newspaper.

A spokeswoman declined to confirm the report, but said in a statement that the mint “has modified the varnish and optimized its manufacturing process to make it more resistant to certain uses observed of the medals by athletes.”

Faced with a deluge of deteriorating medals, the International Olympic Committee has vowed to find replacements. “Damaged medals will be systematically replaced by the Monnaie de Paris and engraved in an identical way to the originals,” it said in a statement.

For LVMH, the Olympics were a coming-out party. It was a major foray into sports, and a moment to promote the company in a way that it had previously avoided, preferring instead to showcase its individual brands. .

“Obviously because it’s the medal, it’s super high profile and everyone is asking the question how does this happen and especially coming from LVMH, whose raison d’être is quality and precision,” said Michael Payne, who devised the I.O.C.’s original marketing strategy.