During the upgrade testing, the Ethereum testnet has experienced client synchronization issues in the past. Parithosh Jayathi stated that due to the low participation of testnet validators, approximately 10% of validators going offline would result in the upgrade losing its finality. The offline validators could be attributed to multiple client node operators not upgrading their software.
Ethereum's Cancun Upgrade (Dencun) Goes Live on Goerli Testnet, Client Synchronization Issue Awaiting Fix