Ireland's Olympic silver medallist Annalise Murphy has returned her medal due to a defect.
At least 100 Olympic athletes say their medals from the 2016 Rio games are defective and are sending them back to be replaced.
Complaints include rusting, flaking and black spots, particularly with the bronze medals.
Games Spokesman Mario Andrada said 7% were affected.
She said: "The most common issue is that they were dropped or mishandled and the varnish has come off and they've rusted or gone black in the spot where they were damaged.
"All 2,488 medals were produced by the Brazilian mint, which has agreed to replace any that are returned."
Murphy's manager Finn Murphy said in a statement: "Annalise received an email from the OCI giving her the option to send her silver medal back for re-finishing or to hold on to it.
"She decided to send it back and dropped it into the OCI a couple of weeks ago.
"The medal was looking a bit grubby but we figured that could be down to people passing it around and even biting it!
"I think the problem was that some of the medals hadn't been finished properly at the beginning."
Mr Murphy said: "Annalise is back on the water. She's training in Dún Laoghaire for the summer and will be going to the World Championships in the Netherlands in October."
A spokesperson for rowers Gary and Paul O'Donovan, who also won silver in Rio, said: "Nothing has come through my channels but I'll get in touch with the lads and double check.
"They're currently at a training camp in the Czech Republic.
"The European Championships are this weekend and after that they'll be off to Poznan for the second stage of the World Cup series. It's all go."
