UUPS Upgrade Successful (event emitted) but Implementation Address Not Updating (BSC Mainnet, Hardhat)

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Hi everyone,

I’m encountering an issue with my upgradeable contract on BSC mainnet using Hardhat and would appreciate any insights.

Context

  • Pattern: UUPS upgradeable contract

  • Network: BSC Mainnet

  • Tooling: Hardhat + OpenZeppelin Upgrades plugin

Issue

I performed an upgrade transaction, and:

  • The transaction succeeds

  • The Upgraded(address indexed implementation) event is emitted

  • The emitted address is the new implementation

However:

  • When I check the implementation using:

    await upgrades.erc1967.getImplementationAddress(PROXY_ADDRESS)

    it still returns the old implementation address

What I Expected

After a successful upgrade, I expect:

  • getImplementationAddress(proxy) to return the new implementation

  • Contract behavior to reflect the updated logic

What Actually Happens

  • Event shows correct new implementation

  • But storage (implementation slot) seems unchanged

  • Contract behavior also does not reflect updates

Additional Notes

  • I verified I am using the correct proxy address

  • The upgrade transaction does not revert

  • No errors are thrown during upgrade

Questions

  1. Is it possible for the Upgraded event to emit even if the implementation slot is not updated?

  2. Could this be related to:

    • Using forceImport incorrectly?

    • Proxy mismatch (e.g., calling upgrade on a different proxy instance)?

    • Storage slot collision or corrupted proxy state?

  3. Is there a way to manually verify the implementation slot directly on-chain?

  4. Has anyone encountered this specifically on BSC?

Any guidance or things I should double-check would be greatly appreciated. Thanks!