One "coordinated restart" apparently wasn't enough, because a second one followed later that day. Developers reportedly didn't know why the blockchain suddenly began to slow, though it followed shortly after validators began adopting a new version of Solana code, pointing to a possible culprit in the new release. The new version had reportedly operated for six months on the testnet before it began to be deployed.
Other theories were also considered, as reported by CoinDesk: "One leading theory was that a 'fat block' gunked up the blockchain's mechanics."
The outage is reminiscent of the ones that plagued the network through 2022, leading some to question whether it could be suitable for replacing critical infrastructure.