There is a news article published today on WRS' exit from the blue macaws project, but it's behind a paywall. The relevant parts:
The two Spix's macaws and four Lear's macaws - both members of the blue macaw family - were returned to Brazil in July, said Dr Sonja Luz, vice-president of conservation, research and veterinary services at Wildlife Reserves Singapore (WRS) in response to queries.
Asked why the birds left Singapore earlier, Dr Luz said the agreement is subject to a review every two years.
"In 2019, developments within the blue macaw project brought new partners and funding, as well as a separate technical cooperation agreement," she said.
Dr Luz added: "The new development brought us to an appropriate juncture to hand over the project to our trusted partners as we continue our conservation focus on protecting threatened wildlife in the South-east Asian region."